How do you effectively blacklist an address when you can just generate a new one? Treat it like a one time pad; unless the government is sending out these black lists in real time (but even then...)
If your address is banned by being downstream, you have to do an in person ID check or whatever and explain where you got the coins from.
Edit:
I have always wondered about the fungability of bitcoin. The case above would mean you have some 'hot' bitcoins that are probably worth less than market value. Someone may buy them with freshly mined ones for an exchange rate < 1.
Another scenario is really old bitcoins from 2010. Would they be worth more to 'collectors' if you can get a nice lineage.