Wisconsin regulators can’t enforce a rule requiring sprinklers in large apartment buildings, Republican Attorney General Brad Schimel said Friday in a victory for builders looking to save on costs. The state Department of Safety and Professional Standards adopted a rule in 2008 that requires sprinklers in apartment buildings built after Jan. 1, 2011, that have more than four units. Gov. Scott Walker signed a law in May of 2011 known as Act 21 that prohibited state agencies from writing rules that are more restrictive than state law. In this case, statutes declare that sprinklers are required in apartment buildings with more than 20 units.