A federal ban on medicinal marijuana use has just been issued, and will apparently override state laws that permit patients to use it legally. This is interesting, since the article states the following:

Under the Constitution, Congress may pass laws regulating a state's economic activity so long as it involves "interstate commerce" that crosses state borders. The California marijuana in question was homegrown, distributed to patients without charge and without crossing state lines.

This would leave it up to states to decide if they wanted to legalize the use of medicinal marijuana. As the article states, there are ten states (Washington included) that permit medicinal marijuana at this time. This ban, however, will allow federal authorities to prosecute regardless of the state's position.