If we’re going to do that, we should just get the TNG to do it. Coast Guard has enough jobs without having to monitor an internal river, and I wonder if it might violate the Passe Comitatus Act.
CG is not part of the Defense Department. They are part of Homeland Security and is chartered with protecting water boundaries of the US. Rio Grande fulfills that definition. They would prolly use aircraft anyway.
The Coast Guard is exempt from the Posse Commitatus Act, since they are not part of DOD. That’s why we’re able to board U.S. flag vessels at our discretion, just because we can.
With the Coast Guard falling under certain Customs laws, we would probably have the most jurisdiction than any other federl agency. (As always, I might add.)