Forum and Music posting - direct download link?

Hello everyone, let’s me make this short . I have known that there are several forums where there are copies of music ( include album, CD ’s tracks , CD’s cover with the publisher name) and movies. To me , it is illegal for those who are uploading and downloading these media content. However , some of the forum’s owners stated that they are not responsible for the posted content and because of the Host or ISP( Internet Service Provider) is out of USA . However , their members who are using ISP from USA , also upload those copyrighted media . My question is who will be responsible ? I am truly apologize if my writing is confusing the readers. Thanks for reading my question.