Historical Rules · 23 January 2015
Rule 801.9
Official source text from the 23 January 2015 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.