Whoa. Back up a second. "Have not rammed"? Uh, Mr. Watson, you have televised to the world your own doing of that very thing, with yourself at the helm personally. Not only that, but there have been many attempts to foul propellers & steering gear. At great risk to your own people's lives.
I'm sure the Japs can tell the more complete story, better than I.
Simultanously, but quitely behind the scenes, while this court filing in the U.S. is wending it's way through the process, the Japs could issue Letter of Marque and Reprisal and equip a couple of vessel with heavy-duty RF jamming gear, powerful enough on any and all frequencies the Sea Shepherd folks might be using.
Cut the satellite up-link first. Jam any SSB they attempted to broadcast on immediately thereafter. Close quarters, board 'em to make arrests, and if encountering anything like armed resistance, sink them, then pick up the survivors. Have an on board brig or jail outfitted with enough holding cells for all Sea Shepherd personnel. (There will be more than one Sea Shepherd vessel around, most likely)
Put the mouthiest ones in chains. Leg irons. Give Watson the full chain-up treatment. Hold him incommunicado. Treat the captives well overall, as per international conventions. Feed them good enough...don't actually force them to eat whale meat, but one could offer them some, hehheh...
Take them to Japan, put them on trial there.
“At great risk to your own people’s lives.”
He has made it clear that some people may die in this endeavor and he thinks that is fine. He is a nutjob, thinking that he is doing God’s will and if people die (on either side) then that’s just collateral damage.