In the US, people have the right to decide a sender may no longer send them snail mail if the sender has sent them obscene materials. It's my understanding tha

In the US, people have the right to decide a sender may no longer send them snail mail if the sender has sent them obscene materials. It's my understanding that case laws has led to obscenity in this context being 100% as defined by the recipient. If you believe content type X is obscene, and someone sends you content type X, you can follow the procedure for reporting obscenity. They are obligated to stop sending you anything.