The Mexican government is now taking legal action against the new Arizona immigration law, filing a brief in support of "Friendly House", the suit brought by the American Civil Liberties Union. The ACLU is also directly collaborating with that government on a related matter; whether this comes as a surprise to them or whether they helped bring it about isn't known. However, it puts the ACLU and other far-left groups, the Mexican government, and the Obama administration all on the same page. From this:

A 28-page amicus curiae brief filed in U.S. District Court says that Mexico has a "substantial and compelling interest" in seeing its diplomatic relations with the U.S. not be "frustrated by the actions of individual U.S. states" and in "ensuring that its citizens are accorded human and civil rights" while they are in the U.S... The brief asks the court to declare SB 1070 "unconstitutional in its entirety."... The brief says SB 1070 raises issues "of great importance to the people of Mexico, including the almost twenty million Mexican workers, tourists and students lawfully admitted to the United States throughout 2009, those already present or who will similarly be admitted to the U.S in the future, and the countless millions affected by international trade, immigration policies and drug violence." ..."If S.B. 1070 takes effect, Mexican citizens will be afraid to visit Arizona for work or pleasure out of concern that they will be subject to unlawful police scrutiny and detention," says the brief.

If that's not bad enough, the brief contains this:

SB 1070 Derails Efforts Towards Comprehensive Immigration Reform
With over eleven million nationals in the U.S., Mexico has a significant interest in U.S. comprehensive immigration reform. The United States is equally interested in Mexico’s involvement. In fact, one of the five immigration principles of the Obama administration is to collaborate with Mexico [1].

This is a good opportunity to indeed highlight how much of the political establishment are collaborateurs. Whenever you mention the Arizona issue or the ACLU suit, point out that the ACLU, the Mexican government, and the Obama administration are all on the same page.

7/1/10 UPDATE: Mexico's request to have their brief considered has been granted (link).

[1] The page the brief footnotes (whitehouse.gov/issues/immigration) has this under "Work with Mexico":

President Obama will promote economic development in Mexico to decrease the economic desperation that leads to illegal immigration.