These users may be legal - you'd have to check the FCC frequency
allocations to be sure.

The marine VHF band is in the middle of the land mobile band - used by
taxis, trucking companies, and other commercial radio services.

They use Channel 68 or 69 in my area.
Truckers have been heard on Ch. 71, and 19a

Looks like they are using Marine Channels according to
the FCC rules!

Oh, well, keeps them off the 10 meter ham bands!
A few years ago I heard outbanders on 28.085
griping about people throwing carriers, but the "carriers"
were hams on code transmission. With the tight bandwidth
of cw receivers, the hams were probaly not even aware of
the interlopers!