U.S. District Senior Judge Frederick Scullin Jr.—the federal judge who struck down the District of Columbia’s ban on carrying handguns in public for self-defense—has a reputation as a no-nonsense jurist who sticks closely to the text of the law.

“He generally has a conservative approach to following the law—conservative in the strictest legal sense: ‘This is what Congress wrote, this is what I’m doing, I’m not in search of ambiguities,’ ” said Edward Menkin, a veteran criminal defense lawyer in Syracuse, N.Y.