President Obama backed the Justice Department’s lawsuit to overturn the Arizona immigration law Wednesday.

The Arizona law, which Arizona Governor Jan Brewer signed in April, requires police to question anyone who appears to be in the country illegally. Critics have called it the strictest immigration law in the United States.

The Justice Department’s lawsuit charges that the new state law, which would take effect July 29, conflicts with federal law and would disrupt immigration enforcement. Obama has previously called the law “poorly conceived” and urged the U.S. Congress to enact national immigration reform.

In a press briefing Wednesday, Press Secretary Robert Gibbs said Obama supports the lawsuit’s claim that it is unconstitutional “to have 50 states making a patchwork of immigration decisions.”

The White House decision to back the lawsuit is a controversial one. According to a May CBS News poll, 52 percent of Americans agree with the law and 17 percent think it doesn’t go far enough prevent illegal immigration.

Obama’s support of the lawsuit follows his speech July 1 about the need for comprehensive immigration reform.