Three cities have filed a federal lawsuit against the Department of Defense, arguing many U.S. service members who are disqualified from gun ownership were not reported to the National Background Check System according to court papers.New York City, San Francisco, and Philadelphia claim the military's broken system for relaying such information helped spur the massacre of 26 people inside a Texas church last month.Local law enforcement officials rely on the FBI's database to conduct background checks on gun permit applications and to monitor purchases.26 Men, women, and children were shot to death in the attack at a church in Sutherland Springs Texas back in November.The shooter was able to buy a gun despite his past criminal convictions of extremely violent domestic abuse.The attorney for the cities argues the database must be up-to-date in order to prevent people from wrongly getting guns.