Erik Prince is back in business. The billionaire founder of mercenary group Blackwater Worldwide is helping set up a special forces battalion in the United Arab Emirates, where he resettled recently as his company faced mounting legal challenges in the U.S. In the desert outside Abu Dhabi, Colombians, South Africans, and more are trained by retired American soldiers and veterans of German and British special operations units. According to their contract, the battalion would work on everything from the securing of nuclear material and urban combat to putting down unarmed protests—but one of the main concerns seems to be defending the UAE, with its small and poorly trained military, against the growing strength of Iran. It's possible that Prince and the UAE's interests parallel those of the United States: Both countries are concerned about growing Iranian influence in the region. But it isn't clear whether Prince is abiding by U.S. laws that prohibit training foreign armies without a contract from the U.S. government, and it isn't clear what his rules of engagement are. Blackwater was notorious for violations of international law, and in April a Federal appeals court reopened a case against four Blackwater guards accused of killing 17 Iraqi civilians in 2007.