Given how much of the oligarch's money has been money-laundered into North America and Europe, something our own greedy politicians disgustingly refused to investigate for the better part of three decades, it should be permanently seized and never returned to them. Instead it should be liquidated and handed over to Ukraine to repair the damage done when this is all over.
I imagine right now it's high anticipation at US Cyber Command, as the guys and girls at the consoles are just waiting for the orders to start pressing buttons & entering codes that put Russia back into the stone age. It can be done. And, in retaliation for Putin's manipulation of events & movements in the West, it absolutely SHOULD be done. Empty ever single bank account inside Russia with one mouse click. Take every penny from the oligarchs and have it disappear forever into a digital black hole.
As Max Brooks once said on Real Time a few years back, when the depths of Putin's involvement with the Trump campaign became more and more apparent, MAKE IVAN BLEED. Brutality is the only language the Russians understand so slap them as hard as we can.