ROME – For months, humanitarian aid workers and Europe’s leaders have been wringing their hands about how to stop the human traffickers who are responsible for the deluge of migrants and refugees making the dangerous crossing from Libyan ports to European shores. There has been talk of everything from destroying smugglers ships to infiltrating the traffickers’ networks, but apparently a more basic plan was also in the works. On Saturday morning Salah Al-Maskhout, a former henchman for Muammar Gaddafi thought to be the mastermind behind the main Mediterranean trafficking ring operating in the seas between North Africa and Europe, was...