I hate to say this (because the French for the most part are idiots} but back in the 80's I think the French wanted to do some nuke testing in the southern pacific... Green Peace bozo's brought in the ship, Rainbow Warrior. The French sent in 4 combat divers to scuttle her... It worked... Might be a good idea...
Or they can do what Canada did. Confiscate the boat for illegal activity and sell it off to with the stipulation that the vessel not be used by Paul Watson types anymore or it will be destroyed on next capture for illegal activity. Use the same laws as are used against deer poachers. They confiscate every item involved in killing of a jacked deer including gun, ammunition,hunting knife, your LEGAL hunting privileges, your car,ATV or truck if involved in transporting carcass, & even the freezer. When the DNR comes a knocking you better hope you aren't frying your venison or you will be frying eggs on a cookie sheet the next day. Political will & Court dockets must start worrying more about these loony terrorists and do the right thing in support of the Quota systems they instituted.