"Washington visitors interested in using marijuana products should be aware of the details of the law regarding purchase, possession, and consumption. There are still significant restrictions for pot possession and use, as well as many practical details to be worked out about how the law will actually be implemented. Washington's weed tourism services are still being developed."
I-502 does not preempt federal law. The production, distribution, sale, possession, and use of marijuana is still against, and may be prosecuted under, US federal law. Marijuana use is also prohibited by most employers.-Angela Brown : Northwest US Travel Expert