the .su domain was made when the soviet union was still around, so that doesn't really break the rules. I would prefer for top level domains to be eternal for a great multitude of reasons
And that's before we get into the really weird not-a-proper-country ones like .im or .pn.
At the time it did not break the rules. It's breaking the rules now because by the original rules it should have been phased out. What makes it survive is a special arrangement.