Arizona’s campaign to push out illegal immigrants heads to the Supreme Court this week, in the second major challenge to federal power the justices have taken up in less than a month.

The Obama administration argues a 2010 Arizona measure aimed at fighting illegal immigration conflicts with federal law. The state law requires police to check the immigration status of people they stop if suspicious of their right be in the U.S.

It also makes it a crime for immigrants without work permits to seek employment.

Both of these provisions, among others, have been blocked by federal courts for interfering with federal immigration laws. Even so, the Arizona statute has sparked copycat measures in Alabama and other states.