What happens if there servers and legal entity is in another country?
I doubt they would have any legal basis for extraditing a non-US-citizen for a SOPA violation, but there have been attempts to pursue charges against foreign citizens for notable DMCA violations if they enter the US, so that could continue to be the case with SOPA. If a US citizen uses a foreign server, I doubt that would shield them from legal action.
If these peers choose to ignore ARIN's edict, it raises a number of troubling questions, mind you - so we don't really want to go that route if we don't have to. But the point is, Canadian ISPs could very well take a stand against the US using ARIN to enforce SOPA overseas.