On October 10, 2007, the US District Court for the Northern District of California granted a preliminary injunction which blocked the implementation of Department of Homeland Security (DHS) regulations designed to make it more difficult for domestic employers to hire illegal immigrants. These strict rules required employers to fire employees whose names and Social Security numbers did not match the records of the Social Security Administration (SSA) or risk heavy fines. The lawsuit was brought by the American Civil Liberties Union (ACLU) and the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO). It argued that the regulations would discriminate against legal immigrants and substantially burden employers. DHS ultimately rescinded the controversial rule in October 2009, although the similar, largely voluntary E-Verify system remains in use.