MEXICO CITY (Reuters) - Mexico s Congress on Friday approved a law that enshrines the use of the army in the country s long war against drug cartels, overriding protests from the United Nations rights body and activists who fear it will encourage abuses by the military. The ruling Institutional Revolutionary Party and some members of the center-right opposition National Action Party backed the bill, which now will head to President Enrique Pena Nieto s desk to be signed into law. Known as the Law of Internal Security, the bill establishes rules for the military s role in battling drug gangs, a conflict that has claimed well over 100,000 lives in the last decade. The military has been mired in several human rights scandals, including extra-judicial killings of suspected gang members and the 2014 disappearance of 43 students near an army base. Supporters of the legislation say it will set out clear rules that limit the use of soldiers to fight crime. Rights groups are not convinced, saying the bill empowers security forces instead of improving the police and could usher in greater abuses and impunity. The United Nations, Amnesty International and Mexican human rights organizations all lobbied lawmakers not to pass the bill. 