diff --git a/src/actions/signup.ts b/src/actions/signup.ts
index 8025c35..b61bfe2 100644
--- a/src/actions/signup.ts
+++ b/src/actions/signup.ts
@@ -66,8 +66,9 @@ export const signup = {
         });
       }
 
+      let memberUuid;
       try {
-        await getJavaUuid(input.teamMember);
+        memberUuid = await getJavaUuid(input.teamMember);
       } catch (_) {
         throw new ActionError({
           code: 'NOT_FOUND',
@@ -85,6 +86,15 @@ export const signup = {
           });
         }
       }
+      if (memberUuid) {
+        const blockedUser = await db.getBlockedUserByUuid({ uuid: memberUuid });
+        if (blockedUser) {
+          throw new ActionError({
+            code: 'FORBIDDEN',
+            message: 'Dein Mitspieler ist für die Registrierung gesperrt. Bitte suche dir einen anderen Mitspieler'
+          });
+        }
+      }
 
       if (!teamDraft) {
         // check if a team with the same name already exists