Sanford, Florida—the city where Trayvon Martin was shot and killed by George Zimmerman—has changed its Neighborhood Watch rules, and will now perform background checks and all volunteers will have to undergo a six-week training program. The police department will also recommend that volunteers not carry firearms. The city’s police chief, Cecil E. Smith, who took over after the previous chief resigned amid the handling of the Martin case, will announce the new rules at a community meeting on Tuesday. The new rules could open the city up to lawsuits, since the state’s gun laws allow licensed gun owners to carry conceal weapons. Zimmerman was acquitted earlier this year of second-degree murder charges.