Historical Rules · 17 June 2011
Rule 702.15d
Official source text from the 17 June 2011 Rules release
A permanent with protection can't be equipped by Equipment that have the stated quality or fortified by Fortifications that have the stated quality. Such Equipment or Fortifications become unattached from that permanent as a state-based action, but remain on the battlefield. (See rule 704, "State-Based Actions.")