As I mentioned[0] a few months ago after the TSA announced the $45 "fee":

   ...The courts have repeatedly struck down limits on domestic travel over the 
   past couple hundred years.

   In fact, the $45 "fee" is an acknowledgment that you aren't required to have 
   special documents to travel within the US. Otherwise, they just wouldn't let 
   you travel.

   So instead, they're making more security theater and punishing you if you 
   don't comply with their demands...

And now the birds are coming home to roost. No real surprise there, IMHO.

[0] https://news.ycombinator.com/item?id=46128346