From the article:
Organized medicine invariably opposes wider scopes of practice and independent practice of nonphysician health professionals, ostensibly not to protect economic turf but to protect the quality of patient care. Curiously, one rarely finds those to be protected by this paternalism vocally on organized medicine’s side.
Not many economists today are buying the medical profession’s position on this issue. More typically, economists lean toward Friedman’s more cynical view. They regard professional licensure of any kind – almost always proposed by the very professionals or occupations to be licensed – mainly as a means to endow the licensees with monopolistic market power.
Source: Uwe E. Reinhardt, "The Dubious Case for Professional Licensing," The New York Times, October 11, 2013