From 1996 to today, 30 states have legalized medical marijuana, as well as Washington, D.C., Guam and Puerto Rico, according to NCSL.org. Of those 30 states, 10 have passed legislation legalizing adult use. Although this trend matches a 2018 Pew Research Center survey suggesting that six out of 10 Americans support marijuana legalization, the United States military still maintains a zero tolerance policy for marijuana use, regardless of form.