CAN-SPAM Act (Controlling the Assault of Non-Solicited Pornography And Marketing Act) of 2003.

Perhaps, auto-forward them to spam@uce.gov w/ some sort of preface that you can't unsubscribe.

Then I'd use the universal unsubscribe button aka report spam

Facebook does the same thing. If you click unsubscribe, you need to login first

I feel like many “unsubscribe” links don’t actually unsubscribe me, so I just block the email addresses as they come in now.

“Please allow up to 48 hours for this change…” nah I’ll just block sender.