You fly the flag of the country your boat is registered in.
The real question is, “In whose name is the boat registered?”
Maybe its on its way to some safe holding harbor, in which case flying a US flag on its way is not a big deal in comparison to stealing it.
But, if it became a US or EU VIP party boat, I’d be enraged. As would Vlad and his friends.
I wonder when it will be on one of the Fed surplus equipment auction websites? Or will the feds just use it as the presidential yacht?
The ship has been seized under sanctions because the profits that paid for the ship can be tied to resources that were stolen from Ukraine. The ship will eventually be auctioned off and the proceeds handed over to Ukraine.