Defense Secretary Chuck Hagel has ordered a review of US military law and of a sexual assault case in which an Air Force general overturned a fellow officer's conviction, the Pentagon said Tuesday.

The move came after an outcry from lawmakers and rights advocates over the case of Lieutenant Colonel James Wilkerson, whose conviction on sexual assault charges and one-year prison sentence was tossed out last month by a senior commander, which is permitted under the military's code.

Hagel has demanded an examination of the case as well as the military rules that grant authority to commanding officers to reverse verdicts, Pentagon spokesman George Little told reporters.

"Secretary Hagel has directed two separate reviews to ensure our military justice system is appropriately protecting victims of sexual assault, as well as dispensing justice for the accused," Little said.

The uproar over the case coincides with a scandal over a spate of sexual assault charges at the Air Force's main training center in Lackland, Texas, as well as growing criticism in Congress over how the military is handling the problem.

A critically-acclaimed documentary, "The Invisible War," which was nominated for an Oscar last month, has also drawn attention to the issue. The film features female service members recounting how survivors suffered reprisals for reporting assaults while perpetrators were not penalized and often received promotions.

The Pentagon said Hagel asked the secretary of the Air Force, a civilian, to examine whether the military code of justice was correctly applied in the Wilkerson case and how the final decision could be made more "transparent."

Lieutenant General Craig Franklin, who had the final say in the Wilkerson court martial, concluded the evidence against the Air Force officer was insufficient to support a guilty verdict. But the military code does not require the general to explain the reasoning behind his decision.

Hagel also directed the Pentagon's top lawyer to assess the military code's Article 60, which gives broad authority to commanding officers in legal cases, and to consider whether changes should be made to the legal provision, after consulting with the chiefs of all the armed services.

"Our service members must know that they are protected from criminal assault by a system of laws that function promptly, fairly, and justly," Little said.

Senator Claire McCaskill, a former prosecutor, has led calls for action in the case and said it has exposed a deep rooted problem inside the armed forces.

"There's a culture issue that's going to have to be addressed here," she said last week. "And what this decision did -- all it did was underline and put an exclamation point behind the notion that if you are sexually assaulted in the military -- good luck."