The Mexican government and 15 other countries [1] have filed a brief supporting those suing Alabama to block that state's new immigration law. The federal judge in the case consolidated the various lawsuits against Alabama, meaning that the American Civil Liberties Union, the Southern Poverty Law Center, the Department of Justice, the Catholic Church, the Methodist Church, the Episcopal Church, and the Mexican government are all involved in the same suit and are all on the same side against the will of the great majority of Americans.

From this:

"They want to make sure their citizens are treated cor­rectly, and they have a sover­eign interest in the way in which immigration law is car­ried out by the United States," said Edward Still, a Birming­ham attorney who filed the briefs on behalf of the nations. "They want to have one immi­gration law and not 50."

..."Mexico has an interest in protecting its citizens and en­suring that their ethnicity is not used as basis for state-sanc­tioned acts of bias and discrim­ination," the brief says.

..."The governments have a substantial and compelling in­terest to ensure that their citi­zens are accorded human and civil rights when present in the United States in accordance with international treaties, the U.S. Constitution and federal immigration law," the 15-nation brief says.

Mexico's interest probably has much less to do with a desire to protect their citizens and much more to do with the fact that their citizens who are in the U.S. illegally send home billions of dollars each year. Those millions of illegal aliens also form a political power base inside the U.S. for the government of Mexico.

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[1] The other countries are: Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Dominican Republic, Ecuador, El Salvador, Guatemala, Hon­duras, Nicaragua, Paraguay, Peru and Uruguay.