Marijuana possession, while made legal in many states now, can still be a basis for denial of your existing or future immigration benefits, even if it never resulted in either a criminal charge or conviction.
Marijuana continues to be a Schedule I narcotic. Simple possession of any Schedule I substance is illegal under 21 U.S.C. § 844. Current Attorney General has rescinded prior guidance accommodating State laws on marijuana, particularly those allowing its possession and use for medical purposes. The Department of Justice’s approach is likely to be mirrored in the consideration of such conduct by U.S. Citizenship and Immigration Services (“USCIS”)
8 U.S.C. § 1182(a)(2)(A)(i)(II) makes inadmissible to the United States a foreign national:
“convicted of, or who admits having committed, or who admits committing acts which constitute the essential elements of .... a violation of (or a conspiracy or attempt to violate) any law or regulation .... relating to a controlled substance (as defined in section 802 of title 21)
Also 8 U.S.C. § 1182(a)(1)(A)(i) makes inadmissible someone determined to be a drug abuser or drug addict, a determination which would be made by a civil surgeon acting under designation by USCIS. USCIS Policy Manual, Volume 8 (Admissibility), Part B Health-Related Grounds of Inadmissibility, Drug Abuse or Drug Addiction. Marijuana still presents a considerable danger for immigrants in the US.