diff --git a/src/controllers/RunnerSelfServiceController.ts b/src/controllers/RunnerSelfServiceController.ts
index 3d2750f..41655ca 100644
--- a/src/controllers/RunnerSelfServiceController.ts
+++ b/src/controllers/RunnerSelfServiceController.ts
@@ -1,6 +1,6 @@
 import { Request } from "express";
 import * as jwt from "jsonwebtoken";
-import { Body, Delete, Get, JsonController, OnUndefined, Param, Post, QueryParam, Req, UseBefore } from 'routing-controllers';
+import { BadRequestError, Body, Delete, Get, JsonController, OnUndefined, Param, Post, QueryParam, Req, UseBefore } from 'routing-controllers';
 import { OpenAPI, ResponseSchema } from 'routing-controllers-openapi';
 import { getConnectionManager, Repository } from 'typeorm';
 import { config } from '../config';
@@ -148,8 +148,11 @@ export class RunnerSelfServiceController {
 	@OpenAPI({ description: 'Create a new selfservice runner in the citizen org. <br> This endpoint shoud be used to allow "everyday citizen" to register themselves. <br> You have to provide a mail address, b/c the future we\'ll implement email verification.' })
 	async registerRunner(@Body({ validate: true }) createRunner: CreateSelfServiceCitizenRunner, @QueryParam("locale") locale: string = "en") {
 		let runner = await createRunner.toEntity();
-
+		if (await this.getRunnerExistsByMail(runner.email)) {
+			throw new BadRequestError("E-Mail already registered")
+		}
 		runner = await this.runnerRepository.save(runner);
+
 		let response = new ResponseSelfServiceRunner(await this.runnerRepository.findOne(runner, { relations: ['scans', 'group', 'group.parentGroup', 'scans.track', 'cards', 'distanceDonations', 'distanceDonations.donor', 'distanceDonations.runner', 'distanceDonations.runner.scans', 'distanceDonations.runner.scans.track'] }));
 		response.token = JwtCreator.createSelfService(runner);
 
@@ -170,6 +173,9 @@ export class RunnerSelfServiceController {
 		const org = await this.getOrgansisation(token);
 
 		let runner = await createRunner.toEntity(org);
+		if (await this.getRunnerExistsByMail(runner.email)) {
+			throw new BadRequestError("E-Mail already registered")
+		}
 		runner = await this.runnerRepository.save(runner);
 
 		let response = new ResponseSelfServiceRunner(await this.runnerRepository.findOne(runner, { relations: ['scans', 'group', 'group.parentGroup', 'scans.track', 'cards', 'distanceDonations', 'distanceDonations.donor', 'distanceDonations.runner', 'distanceDonations.runner.scans', 'distanceDonations.runner.scans.track'] }));
@@ -225,4 +231,14 @@ export class RunnerSelfServiceController {
 
 		return organization;
 	}
+
+	/**
+	 * Checks if a runner already exists
+	 * @param email The runner's email address
+	 * @returns Boolean (true if exists, false if not)
+	 */
+	private async getRunnerExistsByMail(email: string): Promise<boolean> {
+		const runner = await this.runnerRepository.findOne({ email });
+		return runner != undefined
+	}
 }
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