Your argument for navigable breaks down because the FAA determines what is "navigable".
That is determined in Part 77, yes they can rewrite the reg.
If someone is flying an aircraft, that airspace is clearly navigable.
That is not the definition of navigable, look it up in the law. Helicoptors are the only aircraft allowed to regularly fly in non navigable airspace. Other aircraft are allowed if they stay away from buildings and people by 500 feet.
Like it or not, the FAA has the authority.
The law clearly states their authority is in navigable airspace.
If you want to avoid the regulation, your best bet is to buy a 5,000 acre farm someplace, and secede from the union.
We are becoming a totalitarition nation. At some time the later option will become attractive.