diff --git a/api/services/src/organisation.rs b/api/services/src/organisation.rs
index 5aecf65..e17065e 100644
--- a/api/services/src/organisation.rs
+++ b/api/services/src/organisation.rs
@@ -47,6 +47,20 @@ impl OrganisationService {
         Ok(exists)
     }
 
+    pub async fn joined(
+        user: &User,
+        db: &OrmConnection,
+        organisation: Uuid,
+    ) -> Result<bool, OrganisationServiceError> {
+        let exists = organisation_user::Entity::find()
+            .filter(organisation_user::COLUMN.organisation_id.eq(organisation))
+            .filter(organisation_user::COLUMN.user_id.eq(user.id().to_string()))
+            .exists(db)
+            .await?;
+
+        Ok(exists)
+    }
+
     pub async fn create(
         db: &OrmConnection,
         organisation: Organisation,
diff --git a/api/src/routes/organisation.rs b/api/src/routes/organisation.rs
index 7dfa5b3..99457fa 100644
--- a/api/src/routes/organisation.rs
+++ b/api/src/routes/organisation.rs
@@ -25,15 +25,22 @@ enum ApiError {
 
     #[error("organisation does not exists")]
     OrganisationDoesNotExists,
+
+    #[error("organisation already exists")]
+    OrganisationAlreadyJoined,
+
+    #[error("organisation does not exists")]
+    OrganisationNotJoined,
 }
 
 impl IntoResponse for ApiError {
     fn into_response(self) -> Response {
         let status = match &self {
             ApiError::ServiceError(_) => StatusCode::INTERNAL_SERVER_ERROR,
-            ApiError::OrganisationAlreadyExists | ApiError::OrganisationDoesNotExists => {
-                StatusCode::BAD_REQUEST
-            }
+            ApiError::OrganisationAlreadyExists
+            | ApiError::OrganisationDoesNotExists
+            | ApiError::OrganisationAlreadyJoined
+            | ApiError::OrganisationNotJoined => StatusCode::BAD_REQUEST,
         };
 
         warn!("{:?}", self);
@@ -86,6 +93,10 @@ async fn join_organisation(
         return Err(ApiError::OrganisationDoesNotExists);
     }
 
+    if OrganisationService::joined(&user, &state.db_connection, org_uuid).await? {
+        return Err(ApiError::OrganisationAlreadyJoined);
+    }
+
     OrganisationService::join(&user, &state.db_connection, organisation.uuid).await?;
 
     Ok(StatusCode::OK)
@@ -102,6 +113,10 @@ async fn leave_organisation(
         return Err(ApiError::OrganisationDoesNotExists);
     }
 
+    if !OrganisationService::joined(&user, &state.db_connection, org_uuid).await? {
+        return Err(ApiError::OrganisationNotJoined);
+    }
+
     OrganisationService::leave(&user, &state.db_connection, organisation.uuid).await?;
 
     Ok(StatusCode::OK)
diff --git a/api/tests/organisation.rs b/api/tests/organisation.rs
index ce51e82..7cc24c6 100644
--- a/api/tests/organisation.rs
+++ b/api/tests/organisation.rs
@@ -182,10 +182,79 @@ async fn join_unknown_organisation() {
 
 #[tokio::test]
 async fn join_already_joined_organisation() {
-    todo!()
+    let client = get_client().await;
+
+    let organisation_uuid = Uuid::new_v4();
+
+    client
+        .add_organisation_json(json!(
+        {
+            "uuid": organisation_uuid,
+            "name": "Test Organisation",
+        }
+        ))
+        .await;
+
+    client
+        .leave_organisation(json!(
+        {
+            "uuid": organisation_uuid,
+        }
+        ))
+        .await
+        .assert_status_success();
+
+    client
+        .join_organisation(json!(
+        {
+            "uuid": organisation_uuid,
+        }
+        ))
+        .await
+        .assert_status_success();
+
+    let response = client
+        .join_organisation(json!(
+        {
+            "uuid": organisation_uuid,
+        }
+        ))
+        .await;
+
+    response.assert_status_bad_request();
 }
 
 #[tokio::test]
 async fn leave_already_leaved_organisation() {
-    todo!()
+    let client = get_client().await;
+
+    let organisation_uuid = Uuid::new_v4();
+
+    client
+        .add_organisation_json(json!(
+        {
+            "uuid": organisation_uuid,
+            "name": "Test Organisation",
+        }
+        ))
+        .await;
+
+    client
+        .leave_organisation(json!(
+        {
+            "uuid": organisation_uuid,
+        }
+        ))
+        .await
+        .assert_status_success();
+
+    let response = client
+        .leave_organisation(json!(
+        {
+            "uuid": organisation_uuid,
+        }
+        ))
+        .await;
+
+    response.assert_status_bad_request();
 }