I had a tremenjous reply here, but I'll boil it down.
If the pt is a threat to self or others and is AMA, call LE. LE can declare them unfit, sort of like the implied consent of lost consciousness.
If LE says medical transport is neccesary for the pt or public safety and you refuse, you can be arrested or at least cited for endangerment, refusing to follow an officer's order, and maybe either obstructing justice or interfering with an officer. You may be right, but they can do that, and let the court settle it later.
Now, most of this will never happen if people just talk resonably, and sometimes give in to the inevitable if it will not cause harm; make the complaint later. Getting into an officer's face and telling them what they can't do on a scene or the street will almost guarantee you trouble.
As for a supervisor not letting you accept an AMA, now THAT could be false arrest or kidnapping, and who would be responsoble, the supervisor? No, the EMT doing the restraint.
Not rocket science. On the street, being smart or tricky will get you further than making threats you can't enforce or playing trump cards they won't recognize.
PS: blood alcohol is a law enforcement issue, not medical, unless you are officially collecting evidence. Then you get subpoenaed, etc. You want a good set of vitals, a good exam, and someone who will go willingly with you instead of the nice police officer.