Final answer:
Article 112a of the Uniform Code of Military Justice (UCMJ) is where information regarding the possession of or use of illegal substances in the military can be found.
Step-by-step explanation:
The information on the possession of or use of illegal substances in the military can be found under Article 112a of the Uniform Code of Military Justice (UCMJ). This article specifically addresses the wrongful use, possession, distribution, and introduction onto military installations of controlled substances. The UCMJ was codified as the system of military justice to enforce laws for service members, where violation can lead to a court-martial, which is a military court or a trial conducted in the military justice system.
Furthermore, the UCMJ is a result of the powers granted to Congress under Section 8 Clause 14 of the United States Constitution, which permits Congress to set rules for the behavior of the armed forces. Prior to 1951, these rules were known as the "Articles of War," but post-1951 they were redefined and are now encompassed within the UCMJ.