Assault Weapons Ban of 2019 This bill makes it a crime to knowingly import, sell, manufacture, transfer, or possess a semiautomatic assault weapon (SAW) or large capacity ammunition feeding device (LCAFD). The prohibition does not apply to a firearm that is (1) manually operated by bolt, pump, lever, or slide action; (2) permanently inoperable; (3) an antique; or (4) a rifle or shotgun specifically identified by make and model. The bill also exempts from the prohibition the following, with respect to a SAW or LCAFD: importation, sale, manufacture, transfer, or possession related to certain law enforcement efforts, or authorized tests or experiments; importation, sale, transfer, or possession related to securing nuclear materials; and possession by a retired law enforcement officer. The bill permits continued possession, sale, or transfer of a grandfathered SAW, which must be securely stored. A licensed gun dealer must conduct a background check prior to the sale or transfer of a grandfathered SAW between private parties. The bill permits continued possession of, but prohibits sale or transfer of, a grandfathered LCAFD. Newly manufactured LCAFDs must display serial number identification. Newly manufactured SAWs and LCAFDs must display the date of manufacture. The bill requires law enforcement agencies to be notified when a prohibited person attempts to purchase a grandfathered SAW. It also allows a state or local government to use Edward Byrne Memorial Justice Assistance Grant Program funds to compensate individuals who surrender a SAW or LCAFD under a buy-back program.