This is all kind of too reductionist.

The US DHS agents in the US make a choice not to fuss over the airplanes or even cruise ships sailing from US ports to Hawaii and back. They could, but they don't. They probably validate the ship or plane's location via transponder, but it wouldn't even surprise me if they don't do that for regular commercial transport.

This kind of local and specific policy is great and it is enacted in lots of places within US jurisdiction.