I would say - if what you're doing is causing that much of a nuisance that it warrants it investigation then there could be some repercussion. But we're talking sending millions of emails. There are cases where the US / UK or EU have shut down spammers in other countries with the help of the local enforcement agencies.
But that's extreme.
Do you have to? No. There is no jurisdiction across borders.
If you're a respectable site then why why flaunt them? They have normally come about due to massive irritation from users.
Why the question? Which law / practice are you worried about?