Can the Chain of Command confiscate a Soldier's POV keys?

Context. You can't do it arbitrarily, but if a Soldier is drunk and getting into the drivers seat, you BETTER take those keys...

The only time I confiscated keys, as OOD, when a Marine was intoxicated. Was I on shaky ground, maybe... but nobody ever said anything about it the next day when they came to get their keys back.

I have heard of commands revoking a Marine's on-base driving privileges.

No. The Command Cannot confiscate private property. Keys are part of the POV. My previous command decided to take away motorcycle keys from a Soldier that was riding on pink shorts and flip flops out in town. Soldier walked straight to legal and the command received a call from legal telling them to give keys back. Now the Command was able to take the Soldiers MSF card because it was obtain through a class funded by the military. Legal refer to his motorcycle keys as private property.

I need an example for counseling for driving with an expired driver license

Hell, in 1979 when I went to Ft. Dix to attend Drill Sgt School, I'd arrived about 3 weeks before my class date.  I was assigned to my basic training company and for 3 weeks, I was what they called a hard hat.  Doing the job of a drill sgt, learing all I could.  Going home every night.  The first day of school was a Saturday and we were instructed to show up in PT gear.  Our first test was the PT test.  If you didn't pass you didn't go to school.   If you passed, that was the first of 112 tests you had to pass to graduate.  That day we moved into the schools barracks.  Every student lived in the barracks.  We stood inspections every day.  Both inside and outdoors.  You were not allowed off school grounds for any reason even when you were not in school because you were expected to be studying and practicing for your exams.  The only key(s) you were allowed to have were the keys to your wall/foot lockers and that was it.  At the end of the 2nd week we had a huge complete field layout and class A inspection.  If you passed you were allowed to move out of the barracks and life returned to some semblence of normal.  While no one took your keys away, it was understood that you didn't have any keys.  It was a merit school and enough demerits would send you packing.  There are ways to do things that have the same affect as taking away someones car keys.  At least in the day there were.

They can use a MPO (Military Protection Order) to restrict the Military member from driving. MPO's are used like restraining orders also but, it can be used for this kind of thing.