Take Valley Park, Mo., which passed an ordinance requiring city businesses to sign affidavits swearing that they don’t knowingly hire illegal aliens and prohibiting illegal aliens from renting or leasing property. The town got the idea from a similar law passed in Hazelton, Pa., which spread around the Internet on anti-immigration Web sites and became a template for towns and cities across the country. Shaheena Simons, a lawyer at the Mexican American Legal Defense and Educational Fund (MALDEF) in Washington, says at least 50 other cities–in states including California, Alabama, Oklahoma, New York and New Jersey–have either passed similar laws or have them in the works.

Right about now is when you start thinking, how long will it take pro-immigration groups to file a lawsuit? They already have. National immigration advocates like MALDEF and the National Council of La Raza, are quietly helping locals challenge anti-immigration laws in nearly a dozen cities. The ACLU helped shut down the Hazelton law, and this week a court issued a temporary restraining order barring enforcement of the Valley Park ordinance. The judge will decide on Nov. 1 whether to make the injunction permanent, but the city has already decided not to wait that long; the day after the restraining order was issued, Valley Park officials called a special meeting and passed another ordinance that they think will get around the court’s ban. The new measure is now the law–until a judge says otherwise.