Which Army Regulation covers the Uniform Code of Military Justice (UCMJ)?

Army Regulation 27-10 is the correct response as it specifically addresses the Uniform Code of Military Justice (UCMJ). This regulation outlines the Army's judicial and non-judicial processes, detailing how military justice is administered and the framework for addressing violations of military law. The UCMJ serves as the foundational legal code for all members of the armed forces, and Army Regulation 27-10 effectively implements the UCMJ within the Army.

The other options pertain to different aspects of Army regulations. Army Regulation 600-20 deals with command policy and covers issues like equal opportunity and sexual harassment, while Army Regulation 15-6 outlines the procedure for conducting informal investigations. Army Regulation 670-1 governs the wear and appearance of the Army uniform, thus not relating directly to military justice matters.