MADISON, Wis. (AP) – The American Civil Liberties Union has filed a federal lawsuit against Gov. Scott Walker’s administration alleging a police crackdown down on protesters in the state Capitol is unconstitutional.  Walker’s plan to strip most public workers of nearly all their union rights sparked massive protests at the Capitol in 2011. A small group of hard-core protesters still gathers in the building’s rotunda daily to sing and chant against Walker. Capitol Police, an agency Walker controls, began cracking down on the singers in September by issuing scores of citations to group leaders, mostly for failing to obtain permits.  The lawsuit filed Monday alleges the police policy is overbroad and violates the protesters’ right to free expression.  Walker’s administration issued a statement saying permit requirements are constitutional and all groups need them.