The 1976 law prescribed a 2-year mandatory prison sentence for individuals who were in possession of a firearm during the commission of a felony. The law was politically popular both with the public and with many highly influential prosecutors who were instrumental in getting the law passed. Despite the law's specificity and other factors creating conditions which were ideal for implementation, environmental pressures and constraints influenced prosecutors to apply the mandatory sentencing policy selectively and in some cases to apply it selectively to minority offenders. Only 65 percent of the eligible cases were charged with the gun law. In courts in the Detroit area, 70 percent of the eligible cases were charged, while in 19 of the other 21 jurisdictions the law was used in either all or none of the cases. Blacks were significantly more likely to receive the gun law charge than whites; 74 percent of the black defendants and 56 percent of the white defendants faced felony firearm charges. Older defendants and those with prior felony convictions were also significantly more likely to be charged with the gun law. Thus, local political conditions were stronger influences on the implementation than were original policy standards or State-level support. The recipients of the felony firearms charge tended to be black offenders, persistent offenders, or both. Tables and a list of 23 references are provided.