Dependency on illegal drugs, as well as a history of dependence on alcohol will keep you out of the military. However, different branches of the military have different limitations to “non-hard” drugs you may have experimented with. For example, the Air Force requires those to admit to smoking marijuana more than 25 times to have a waiver to join, while those who admit to smoking 15-25 times are required to have a Drug Eligibility Determination, an examination by a Drug and Alcohol Specialist. https://usmilitary.com/military-recruiting-drug-use-can-you-still-join/