The push by congressional Democrats to bar suspected terrorists from acquiring guns and explosives has focused renewed attention on the government's secretive terrorist watch lists, which have grown exponentially since the 9/11 attacks. Since the mass shooting in a gay nightclub in Orlando on June 12, Democrats have endorsed various measures to get weapons out of the hands of people on the lists. The Orlando shooter, Omar Mateen, had been on the FBI's terrorist watch list but was removed in 2014. His was one of approximately 800,000 names in that database, the most prominent of at least seven overlapping watch lists. The government does not release the exact number of watch lists or the specific criteria for getting on them. The no-fly list ... contained 16 people on Sept. 11, 2001. By 2014, it had grown to about 64,000 people. Civil liberties advocates [say] the watch lists are riddled with inaccurate and outdated information, nearly impossible to get off and stigmatize the people on them. The largest watch list is The Terrorist Identities Datamart Environment (TIDE), maintained by the National Counterterrorism Center. As of August 2014, it contained about 1.1 million names. The FBI's Terrorist Screening Center ... maintains what is known as the government's consolidated Terrorist Watchlist." It contains about 800,000 names. Last year, [a] federal judge ruled that the government's lack of effective procedures for people to challenge their inclusion on the no-fly list was unconstitutional.