It's true that the DEA hired "bounty hunters" but not American "bounty hunters". In 1990, they hired Mexican nationals to snatch Dr. Humberto Alvarez-Machain and Javier Vasquez Velasco and bring them back to the U.S. (See Old Puzzles, Puzzling Answers: The Alien Tort Statute and Federal Common Law in Sosa v. Alvarez-Machainm" by Mark K. Moller) This is an important and significant difference.
Let this be a lesson to all American Bounty Hunters: Whatever you do, do not arrest Osama Bin Ladin and bring him to justice in the U.S.! Our grateful government will roll over on you in a heartbeat and send you to (fill in the blank) Yemen, Saudi Arabia, Syria or Pakistan to face Islamic justice. No good deed goes unpunished in the Bureacratic States (BS) of America!