Washington ? A federal judge dismissed all charges Thursday against five Blackwater Worldwide security guards accused of killing unarmed Iraqi civilians in a crowded Baghdad intersection in 2007.

Citing repeated government missteps, U.S. District Judge Ricardo Urbina dismissed a case that had been steeped in international politics. The shooting in busy Nisoor Square left 17 Iraqis dead and inflamed anti-American sentiment abroad. The Iraqi government wanted the guards to face trial in Iraq and officials there said they would closely watch how the U.S. judicial system handled the case.

Urbina said the prosecutors ignored the advice of senior Justice Department officials and built their case on sworn statements that had been given under a promise of immunity. Urbina said that violated the guards’ constitutional rights. He dismissed the government’s explanations as “contradictory, unbelievable and lacking in credibility.”