It is a Constitutional issue because the court has consistently upheld that, as part of a right to freely travel, Americans cannot be deprived of use of the com

It is a Constitutional issue because the court has consistently upheld that, as part of a right to freely travel, Americans cannot be deprived of use of the common means of travel of the day without due process. The kind of de facto prohibition on travel you are proposing has been attempted by the government several times in the past in a variety of contexts and the courts have never looked kindly upon it. The court views these "you can still freely travel, but you'll have to walk" style arguments from the government as a transparent attempt to deprive individuals of a well-established Constitutional right absent due process.