I never disagree with the US Code, it outweighs me.(G)
I think we agree with the basics behind the problem, and the (cynic alert) intentional confusion. After all, if the USCG is/was always a military organization, they'd have a problem. "We the people" are exempt from the military chain of command. If the SecDef himself walks up to me and says "Si, step out of the car." I can say "Hey dude, go play with a monkey and get out of my way." And that's fully legal and proper, because as a military officer, he's got no authority over a civilian. And no repercussions to me.
But on the other hand, if an administrative agent of the government (like the IRS or USCG) tells me to do something, there are penalties for failing to comply. Which is why it is inadvisable to tell a Coastie "No, you may not board my vessel and my life jackets and fire extinguishers are none of your business."
They can't have it both ways, either they are military and required to keep hands-off, or they are administrative and CAN enforce administrative law. Whether they've finagled that perhaps by making the USCG full time military who are "lent" to the administrative DHS, or full time administrative who are lent to the DoD, could be another one of those "distinction without a difference" issues. They've still got a dual identify, dual roles, and arguably a congressional-induced split personality disorder. (And I've heard from enough Coasties who would be very much happier if Congress would just let them go back to SAR and safety and let the gung-ho's join that other Navy!)
Very much like the argument about smartphones, encryption, and the border services. If I'm in the US, there's that pesky amendment that was meant to prevent King George's own men, on his own highways, from being able to search my carriage for papers of revolt and sedition. Mine is mine, absent want and warrant. But no, they say you're not in the US and haven't got those rights until AFTER the search. Um, no, can't have it both ways. Having read and agreed with Machiavelli long ago, I can only say these things make me very worried for the longer term of our frail republic. Especially because of the way they attempt to sneak so many changes by, without the burning light of day.