Washington State yes
Looks like WA is more respectful of the 2nd Amendment than fedgov (and some FReepers, sadly). From the WA state website =>
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May I purchase a gun if I am a medical marijuana patient in the database?
The medical marijuana authorization database is in no way connected to any other system and does not affect your right to purchase or carry a gun. However, under federal law, marijuana possession is illegal for both recreational and medical use. The federal law affects gun ownership. It is unlawful for a firearms dealer to sell or give a gun to a person who uses or is addicted to a controlled substance that is illegal under federal law.