Washington’s state Capitol was closed to the public on Tuesday due to security concerns as Gov. Jay Inslee signed into law a bill prohibiting the sale of AR-15s and more than 50 other types of assault weapons. The law will take effect immediately, making Washington the 10th state to enact such a ban. “These weapons of war, assault weapons, have no reason other than mass murder,” Inslee said at the ceremony, according to The Seattle Times. “Their only purpose is to kill humans as rapidly as possible in large numbers.” The ban, which applies to the sale, manufacture, and importation of 62 different gun models, does not affect weapons that people already own. At least one group opposing the measure has already filed a federal lawsuit seeking to have the law deemed unconstitutional. It’s also likely to face a legal challenge from the National Rifle Association, which sued Illinois in January over a similar law. “We are not intimidated by the NRA,” Inslee said at the ceremony.