One of the challenges facing Washington and other states that try to regulate marijuana is keeping weed from being used on federal property, but officials say it's not clear how to discourage that.
An Associated Press analysis of federal court data shows that at least 27,700 people have been cited for having pot on federal land since 2009.
The number is small compared to the hundreds of millions of annual visitors to federal land.
Karen Strand, a 36-year-old medical marijuana patient, was cited for having 2 grams of marijuana in Olympic National Park this summer.
Strand and others say being charged for having tiny amounts of marijuana belies the federal government's assertions that it has "bigger fish to fry" than people who use pot in compliance with state law.