What is Leahy vetting of foreign security forces?

According to Section 502B of the FAA, a principal goal of U.S. foreign policy shall be to promote the increased observance of internationally recognized human rights by all countries. This policy goal is in accordance with both international obligations set forth in the UN Charter and with the constitutional heritage and tradition of the U.S. to promote and encourage increased respect for human rights and fundamental freedoms throughout the world regardless of race, sex, language or religion. In the absence of a Presidential certification to Congress, no SA may be provided to any country in which the government engages in a consistent pattern of gross violations of internationally recognized human rights.

No assistance (includes both articles and training) authorized by the FAA or the AECA will be made available to any unit of the security forces of a country if the Secretary of State has credible information that such unit has committed a gross violation of human rights. Funding may be provided once the Secretary determines and reports to Congress that the affected country is taking effective measures to bring the responsible members of the security forces unit to justice [Section 620M, FAA]. This is commonly referred to as the Leahy Amendment with the process entitled Leahy Vetting. DoW funding for U.S. exercises or training with foreign security force or police units are likewise restricted. Section 1204, NDAA, FY 2015, P.L. 113-291, codified a parallel rule: the Department of War may not provide training, equipment or other assistance to a unit when there is credible information that it committed a gross violation of human rights [10 U.S.C. 362]. Foreign security force members and units nominated for any U.S.-funded training are vetted before the training starts.