Gay rights champion Lady Gaga is now taking on illegal immigration and Arizona's controversial crackdown in particular: The singer, in Mexico City for two shows, smacked the law yesterday, saying, "I don't stand by many of those unjust immigration laws in my country." She said she wrote "Americano" as a response, reports the AP. Gaga next heads to American Idol, reports the New York Post, where she'll mentor the remaining four contestants on Wednesday's show. (More Lady Gaga stories.)