diff --git a/app/challenges-platform/index.ts b/app/challenges-platform/index.ts
index 042382b..c8e8239 100644
--- a/app/challenges-platform/index.ts
+++ b/app/challenges-platform/index.ts
@@ -1,12 +1,12 @@
 export {
+  AccessibleChallengesService,
   ChallengesService,
   ParticipantsService,
   ReviewsService,
   SubmissionService,
-  AccessibleChallengesService,
 } from "./services";
-import { Transformer } from "./models";
 import { transformers } from "../../config/challenges-platform/transformers";
+import { Transformer } from "./models";
 import { BaseTransformer } from "./models/Transformer";
 
 class ChallengesPlatform {
diff --git a/app/challenges-platform/models/index.ts b/app/challenges-platform/models/index.ts
index f6b9bc5..7a8e7a9 100644
--- a/app/challenges-platform/models/index.ts
+++ b/app/challenges-platform/models/index.ts
@@ -1,4 +1,4 @@
-export { Challenge, Format, Evaluation } from "./Challenge";
+export { Challenge, Evaluation, Format } from "./Challenge";
 export { Participant } from "./Participant";
 export { Review, Status } from "./Review";
 export { Submission } from "./Submission";
diff --git a/app/challenges-platform/services/accessible-challenges-service.ts b/app/challenges-platform/services/accessible-challenges-service.ts
index afeb5d7..0e6e2a0 100644
--- a/app/challenges-platform/services/accessible-challenges-service.ts
+++ b/app/challenges-platform/services/accessible-challenges-service.ts
@@ -1,7 +1,7 @@
-import { accessibleChallenges } from "../../../db/schema";
-import { Ok, Result } from "ts-results";
 import { eq } from "drizzle-orm";
+import { Ok, Result } from "ts-results";
 import { db } from "../../../db";
+import { accessibleChallenges } from "../../../db/schema";
 import { Challenge, Participant } from "../models";
 
 export const count = async (
diff --git a/app/challenges-platform/services/challenges-service.ts b/app/challenges-platform/services/challenges-service.ts
index f702638..d17196d 100644
--- a/app/challenges-platform/services/challenges-service.ts
+++ b/app/challenges-platform/services/challenges-service.ts
@@ -1,10 +1,10 @@
 import { eq } from "drizzle-orm";
-import { Ok, Err, Result } from "ts-results";
-import { Challenge, Format, Evaluation } from "../models/Challenge";
+import { Err, Ok, Result } from "ts-results";
+import { uuid } from "../../../app/common";
 import { db } from "../../../db";
 import { challenges } from "../../../db/schema";
-import { uuid } from "../../../app/common";
 import { challengesPlatform } from "../index";
+import { Challenge } from "../models/Challenge";
 
 export const findByUuid = async (
   id: string,
diff --git a/app/challenges-platform/services/participants-service.ts b/app/challenges-platform/services/participants-service.ts
index 07dbe2f..ed9f9d9 100644
--- a/app/challenges-platform/services/participants-service.ts
+++ b/app/challenges-platform/services/participants-service.ts
@@ -1,9 +1,9 @@
 import { eq } from "drizzle-orm";
-import { Ok, Err, Result } from "ts-results";
-import { Participant } from "../models/Participant";
+import { Err, Ok, Result } from "ts-results";
+import { uuid } from "../../../app/common";
 import { db } from "../../../db";
 import { participants } from "../../../db/schema";
-import { uuid } from "../../../app/common";
+import { Participant } from "../models/Participant";
 
 export const findByUuid = async (
   id: string,
diff --git a/app/challenges-platform/services/reviews-service.ts b/app/challenges-platform/services/reviews-service.ts
index b221159..8feaecb 100644
--- a/app/challenges-platform/services/reviews-service.ts
+++ b/app/challenges-platform/services/reviews-service.ts
@@ -1,9 +1,9 @@
 import { eq } from "drizzle-orm";
-import { Ok, Err, Result } from "ts-results";
-import { Review, Status } from "../models/Review";
+import { Err, Ok, Result } from "ts-results";
+import { uuid } from "../../../app/common";
 import { db } from "../../../db";
 import { reviews } from "../../../db/schema";
-import { uuid } from "../../../app/common";
+import { Review, Status } from "../models/Review";
 
 export const findByUuid = async (
   id: string,
@@ -29,7 +29,15 @@ export const create = async (
   body: string,
 ): Promise<Result<Review, Error>> => {
   // TODO: add a check to make sure the submission exists
-  // TODO: check if submission has already been approved or rejected, handle accordingly
+
+  const check = await db
+    .select()
+    .from(reviews)
+    .where(eq(reviews.submissionId, submissionId));
+
+  if (check.length > 0) {
+    return Err(new Error("Submission has already been reviewed"));
+  }
 
   const id = uuid.create();
 
diff --git a/app/challenges-platform/services/submissions-service.ts b/app/challenges-platform/services/submissions-service.ts
index 6fbbf02..55800c2 100644
--- a/app/challenges-platform/services/submissions-service.ts
+++ b/app/challenges-platform/services/submissions-service.ts
@@ -1,15 +1,15 @@
 import { eq } from "drizzle-orm";
-import { Ok, Err, Result } from "ts-results";
+import { Err, Ok, Result } from "ts-results";
+import { challengesPlatform } from "..";
+import { uuid } from "../../../app/common";
 import { db } from "../../../db";
 import { submissions } from "../../../db/schema";
-import { uuid } from "../../../app/common";
 import { Challenge, Participant, Submission } from "../models";
 import {
   AccessibleChallengesService,
   ChallengesService,
   ParticipantsService,
 } from "../services";
-import { challengesPlatform } from "..";
 
 export const findByUuid = async (
   id: string,
diff --git a/config/challenges-platform/transformers.ts b/config/challenges-platform/transformers.ts
index 891de52..dd231a2 100644
--- a/config/challenges-platform/transformers.ts
+++ b/config/challenges-platform/transformers.ts
@@ -1,7 +1,7 @@
-import { GithubIssueTransformer } from "../../app/event-management/models/GithubIssueChallenge";
+import { Transformer } from "../../app/challenges-platform/models";
 import { FlagTransformer } from "../../app/event-management/models/FlagChallenge";
+import { GithubIssueTransformer } from "../../app/event-management/models/GithubIssueChallenge";
 import { PhotoTransformer } from "../../app/event-management/models/PhotoChallenge";
-import { Transformer } from "../../app/challenges-platform/models";
 
 export const transformers: { [name: string]: typeof Transformer } = {
   flag: FlagTransformer,
diff --git a/config/express/index.ts b/config/express/index.ts
index d69f197..3f2499f 100644
--- a/config/express/index.ts
+++ b/config/express/index.ts
@@ -1,7 +1,7 @@
-import express, { Express } from "express";
 import cors from "cors";
 import dotenv from "dotenv";
-import { notFound, errorHandler } from "./middleware";
+import express, { Express } from "express";
+import { errorHandler, notFound } from "./middleware";
 import { default as restRouter } from "./router";
 
 dotenv.config();
diff --git a/db/index.ts b/db/index.ts
index 66e96a5..0c2ed70 100644
--- a/db/index.ts
+++ b/db/index.ts
@@ -1,9 +1,9 @@
+import Database from "better-sqlite3";
+import dotenv from "dotenv";
 import {
   drizzle,
   type BetterSQLite3Database,
 } from "drizzle-orm/better-sqlite3";
-import Database from "better-sqlite3";
-import dotenv from "dotenv";
 
 import * as schema from "./schema";
 
diff --git a/drizzle.config.ts b/drizzle.config.ts
index 04fcdbf..74f0214 100644
--- a/drizzle.config.ts
+++ b/drizzle.config.ts
@@ -1,5 +1,5 @@
-import type { Config } from "drizzle-kit";
 import dotenv from "dotenv";
+import type { Config } from "drizzle-kit";
 
 dotenv.config();
 
diff --git a/test/challenges-platform/factories/accessible-challenge-factory.ts b/test/challenges-platform/factories/accessible-challenge-factory.ts
index c048c9b..1318948 100644
--- a/test/challenges-platform/factories/accessible-challenge-factory.ts
+++ b/test/challenges-platform/factories/accessible-challenge-factory.ts
@@ -1,11 +1,11 @@
-import { challengeFactory } from "./challenge-factory";
-import { participantFactory } from "./participant-factory";
 import {
   Challenge,
   Participant,
 } from "../../../app/challenges-platform/models";
 import { db } from "../../../db";
 import { accessibleChallenges } from "../../../db/schema";
+import { challengeFactory } from "./challenge-factory";
+import { participantFactory } from "./participant-factory";
 
 export const accessibleChallengeFactory = async ({
   challenge,
diff --git a/test/challenges-platform/factories/participant-factory.ts b/test/challenges-platform/factories/participant-factory.ts
index 5b1c2f2..8d4945e 100644
--- a/test/challenges-platform/factories/participant-factory.ts
+++ b/test/challenges-platform/factories/participant-factory.ts
@@ -1,5 +1,5 @@
-import { ParticipantsService } from "../../../app/challenges-platform/services";
 import { Participant } from "../../../app/challenges-platform/models";
+import { ParticipantsService } from "../../../app/challenges-platform/services";
 
 export const participantFactory = async (
   email?: string,
diff --git a/test/challenges-platform/factories/submission-factory.ts b/test/challenges-platform/factories/submission-factory.ts
index b715f4a..33930fc 100644
--- a/test/challenges-platform/factories/submission-factory.ts
+++ b/test/challenges-platform/factories/submission-factory.ts
@@ -1,11 +1,11 @@
-import { challengeFactory } from "./challenge-factory";
-import { participantFactory } from "./participant-factory";
+import { SubmissionService } from "../../../app/challenges-platform";
 import {
   Challenge,
   Participant,
   Submission,
 } from "../../../app/challenges-platform/models";
-import { SubmissionService } from "../../../app/challenges-platform";
+import { challengeFactory } from "./challenge-factory";
+import { participantFactory } from "./participant-factory";
 
 export const submissionFactory = async ({
   participant,
diff --git a/test/challenges-platform/models/Transformer.test.ts b/test/challenges-platform/models/Transformer.test.ts
index a2ed3e8..6409700 100644
--- a/test/challenges-platform/models/Transformer.test.ts
+++ b/test/challenges-platform/models/Transformer.test.ts
@@ -1,9 +1,9 @@
-import { BaseTransformer } from "../../../app/challenges-platform/models/Transformer";
 import {
   Challenge,
   Evaluation,
   Format,
 } from "../../../app/challenges-platform/models";
+import { BaseTransformer } from "../../../app/challenges-platform/models/Transformer";
 
 describe("BaseTransformer", () => {
   describe("newChallenge", () => {
diff --git a/test/challenges-platform/services/accessible-challenges-service.test.ts b/test/challenges-platform/services/accessible-challenges-service.test.ts
index 844b2d6..b2cd305 100644
--- a/test/challenges-platform/services/accessible-challenges-service.test.ts
+++ b/test/challenges-platform/services/accessible-challenges-service.test.ts
@@ -1,7 +1,7 @@
+import { AccessibleChallengesService } from "../../../app/challenges-platform";
+import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
 import { challengeFactory } from "../factories/challenge-factory";
 import { participantFactory } from "../factories/participant-factory";
-import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
-import { AccessibleChallengesService } from "../../../app/challenges-platform";
 
 describe("AccessibleChallengesService", () => {
   describe("count", () => {
diff --git a/test/challenges-platform/services/challenges-service.test.ts b/test/challenges-platform/services/challenges-service.test.ts
index 9e15a09..fa4c5f5 100644
--- a/test/challenges-platform/services/challenges-service.test.ts
+++ b/test/challenges-platform/services/challenges-service.test.ts
@@ -1,9 +1,10 @@
-import { ChallengesService } from "../../../app/challenges-platform";
-import { challengeFactory } from "../factories/challenge-factory";
-import { CustomTransformer, CustomChallenge } from "../custom-transformer";
-import { challengesPlatform } from "../../../app/challenges-platform";
-import { desc } from "drizzle-orm";
+import {
+  ChallengesService,
+  challengesPlatform,
+} from "../../../app/challenges-platform";
 import { uuid } from "../../../app/common";
+import { CustomChallenge, CustomTransformer } from "../custom-transformer";
+import { challengeFactory } from "../factories/challenge-factory";
 
 describe("ChallengesService", () => {
   describe("findByUuid", () => {
diff --git a/test/challenges-platform/services/participants-service.test.ts b/test/challenges-platform/services/participants-service.test.ts
index 6bbdd58..8fcdf8b 100644
--- a/test/challenges-platform/services/participants-service.test.ts
+++ b/test/challenges-platform/services/participants-service.test.ts
@@ -1,6 +1,6 @@
 import { ParticipantsService } from "../../../app/challenges-platform";
-import { participantFactory } from "../factories/participant-factory";
 import { uuid } from "../../../app/common";
+import { participantFactory } from "../factories/participant-factory";
 
 describe("ParticipantsService", () => {
   describe("create", () => {
diff --git a/test/challenges-platform/services/reviews-service.test.ts b/test/challenges-platform/services/reviews-service.test.ts
index f891820..235a7ea 100644
--- a/test/challenges-platform/services/reviews-service.test.ts
+++ b/test/challenges-platform/services/reviews-service.test.ts
@@ -1,11 +1,9 @@
 import { ReviewsService } from "../../../app/challenges-platform";
 import { Status } from "../../../app/challenges-platform/models";
 import { uuid } from "../../../app/common";
+import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
 import { reviewFactory } from "../factories/review-factory";
-import { challengeFactory } from "../factories/challenge-factory";
-import { participantFactory } from "../factories/participant-factory";
 import { submissionFactory } from "../factories/submission-factory";
-import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
 
 describe("ReviewsService", () => {
   describe("create", () => {
@@ -29,6 +27,31 @@ describe("ReviewsService", () => {
         expect(result.val.comment).toBe(body);
       });
     });
+    describe("when submission has already been reviewed", () => {
+      it("returns an error", async () => {
+        const [challenge, participant] = await accessibleChallengeFactory();
+        const submission = await submissionFactory({
+          challenge: challenge,
+          participant: participant,
+        });
+        const body = "Nice work";
+        await reviewFactory({
+          submission: submission,
+          body: body,
+        });
+
+        const result = await ReviewsService.create(
+          Status.APPROVED,
+          submission.id,
+          body,
+        );
+
+        expect(result.err).toBe(true);
+        expect(result.val.toString()).toBe(
+          "Error: Submission has already been reviewed",
+        );
+      });
+    });
     describe("when submission does not exist", () => {
       it("returns an error", async () => {
         const invalidId = -1;
diff --git a/test/challenges-platform/services/submissions-service.test.ts b/test/challenges-platform/services/submissions-service.test.ts
index 6c6132f..a4a4779 100644
--- a/test/challenges-platform/services/submissions-service.test.ts
+++ b/test/challenges-platform/services/submissions-service.test.ts
@@ -2,10 +2,10 @@ import {
   ChallengesService,
   SubmissionService,
 } from "../../../app/challenges-platform";
+import { uuid } from "../../../app/common";
+import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
 import { challengeFactory } from "../factories/challenge-factory";
 import { participantFactory } from "../factories/participant-factory";
-import { accessibleChallengeFactory } from "../factories/accessible-challenge-factory";
-import { uuid } from "../../../app/common";
 
 describe("SubmissionService", () => {
   describe("findByUuid", () => {
diff --git a/test/event-management/models/FlagChallenge.test.ts b/test/event-management/models/FlagChallenge.test.ts
index 0fac1a7..c653853 100644
--- a/test/event-management/models/FlagChallenge.test.ts
+++ b/test/event-management/models/FlagChallenge.test.ts
@@ -1,7 +1,9 @@
-import { FlagChallenge } from "../../../app/event-management/models/FlagChallenge";
-import { FlagChallengeSubmission } from "../../../app/event-management/models/FlagChallenge";
 import { Format } from "../../../app/challenges-platform/models";
-import { FlagTransformer } from "../../../app/event-management/models/FlagChallenge";
+import {
+  FlagChallenge,
+  FlagChallengeSubmission,
+  FlagTransformer,
+} from "../../../app/event-management/models/FlagChallenge";
 import { challengeFactory } from "../../challenges-platform/factories/challenge-factory";
 import { participantFactory } from "../../challenges-platform/factories/participant-factory";