India, Dec. 9 -- Mayor-elect Zohran Mamdani is facing early turbulence in the lead-up to his Jan. 1 swearing-in, after one of his transition team picks ignited questions from law-enforcement groups and conservative commentators. The blowback centers on his decision to pick a controversial figure for the committees shaping his public safety and criminal legal system agenda. The individual in question is Mysonne Linen, a rapper-turned-activist with a criminal past.

The appointment first surfaced publicly in a late November Instagram post by the social-justice organization Until Freedom, which praised Mamdani for bringing community voices directly into policy discussions. But as news spread, police unions, advocacy groups and former NYPD of...