When we look at the history and nature of dry needling, it is pretty obvious that dry needling is basically a simplied version of acupunture. There is no history of PT using needle puncture technique to treat diseases, but acupuncturist has done it for thousands of years. Dry needing is nothging but the acupuncture using the Ashi points. So, it apparently should not be within the scope of practice of PT. 

Physical therapy is a very broad concept, and its scope should not be expanded at will. It can overlap with massage therapy, chiropractics, manual therapy and many other fields, and will cause lots of confusion and unprofessional behavior. Acupunture requires tons of education, and any therapy using needle puncture techique should stay within the scope of practice of acupunctrure.