What does the phrase 'law-abiding, responsible citizens' mean?

QUESTIONS PRESENTED Two important, unresolved federal questions arose from this Court’s landmark decision, District of Columbia v. Heller, 554 U.S. 570 (2008) (“Heller” throughout). The questions resonate throughout the circuit courts with uneven resolution and application, adversely affecting millions of felons including Petitioner, that have served their sentences and have returned to free society, living responsible lives in full compliance with the law. Depending on how these questions are answered, determines whether a felon is entitled to lodge an as-applied challenge to the constitutionality of a felon disarmament law such as 18 U.S.C. §922(g)(1). The questions presented are as follows: 1. What does the phrase “law-abiding, responsible citizens” mean? 2. What does it mean to say that “longstanding prohibitions on the possession of firearms by felons” are “presumptively lawful regulatory measures?”