Not in international waters. But within territorial waters of this country or in countries which allies have agreed to act on behalf of Ukraine's or America's interests they can intervene. The U.S and other countries have to have done their homework though. You can't just be seizing ships without having validly identified the carrier as a transporter or any such carriers and given notice that they are banned from your waters. etc, etc. It can get complicated but the government is supposed to be able to do complicated things. If you are committed you plow through those requirements. Biden was never committed. And if you are not committed your intelligence agencies are not tracking movements. Don't be like that. Not to get too far into the weeds but one of the primary goals is to scare the bejesus out of the insurers of the ships such that they are worried about claims. Then they have incentives to keep their insured ships away from this involvement or their coverage anyway.
The way to go about this is to stop the ghost ships for maritime safety checks. Most of these ghost ships are not in good shape and violate numerous maritime safety laws and regulations. Baltic nations have already done this -- they stopped Russian ghost ships which are in the worst shape then took them to port and docked them. They are demanding the owners show up and fix numerous safety items before the ship is allowed to leave the port. Seeing that the ownership is less then transparent and the ships are not worth repairing (and are near end of life) -- the ships will be docked forever and never fixed. I have previously posted some articles about this. What the western nations need to do is extend maritime safety inspections of Russian ghost ships world-wide. Stop all the ships for safety inspections and take them to port when they fail. All of it totally legal under international law.
P.s he was wrong recently by a lot. Few yrs ago, on JRShow, claimed that vatniks would quit after 500k of KIA's