THEY should be worried more about what YOU might do. Sending that crap to you is cold hard evidence of harassment. Even you said in your first post if BIL continued, you'd get a restraining order. A RO doesn't look very good on someone's record at all.
It reminds me of the time my exhusband texted me a sex joke after we were divorced AND when I was STILL working at his business! It upset me at first, but after I thought about it a brilliant thought came to mind.. hmm... We're not married anymore, and as of right now, I am his employee... I could nail his ass for sexual harassment.