They have to have a CG team, or fly one in. LEDET's or TACLET's. Navy can't enforce stuff like that. Without it being a act of aggression or war.
So a quick sat phone call to State Dept...they call the country the vessels is flagged with. That country quickly denies that they know of said vessel to keep sanctions from being imposed. Basically their own country say's "Never heard of them" and poof you have a stateless vessel (pirate) and then you send in the boarding team.
If you look at the boarding team boats even though they are Navy craft, you'll see they have to fly a CG ensign and have a CG Boarding Officer on the prize crew. Little know much feared Shallow Water Sailors
.-WW