Historical Rules · 5 October 2018
Rule 801.9
Official source text from the 5 October 2018 Rules release
An Equipment can’t equip an object outside its controller’s range of influence, and a Fortification can’t fortify an object outside its controller’s range of influence. If an Equipment or Fortification is attached to an illegal permanent, it becomes unattached from that permanent but remains on the battlefield. This is a state-based action. See rule 704.