technically you could try putting RETURN TO SENDER on all your junk mail and put them back in a blue collection box.
https://faq.usps.com/s/article/What-Options-Do-I-Have-Regard...
https://faq.usps.com/s/article/What-Options-Do-I-Have-Regard...
On the one hand it's definitely harassment to find out someone's address just to send them things they don't want for the purposes of changing their behavior. On the other hand, that's their business model.