 Complete the following phrase:  One provision of the Gun Control Act of 1968 codified at 18 U.S. Code  922g criminalizes firearms purchases by, and firearms sales to, people who have renounced United States citizenship. This provision, along with similar treatment for people adjudged mentally defective or dishonorably discharged from the U.S. Armed Forces, and a restriction on mail-order firearms sales, was aimed at preventing a repeat of the circumstances which allowed Lee Harvey Oswald to obtain the rifle which he used to 