URL groups protection

Hello... In my website, I have a subdomain forum called foro.mydomain.com and I would like to avoid access to the forum for users that are not subscribed to my membership site. So, I added that url to url grupos, and then put this into negative rules for strangers, but the visitor still can get into the forum. What am I doing wrong here or how this works for specific urls?

Thankyou in advance...