The Honolulu Police Department is ordering medical marijuana cardholders to surrender their firearms within a 30-day window of time. KITV reports that Honolulu police are doing this via letters to cardholders demanding they "surrender weapons, permits, and ammunition to HPD or to transfer ownership."
On November 28 The Honolulu Star reported that police have been sending letters throughout the year and the one dated November 13 was signed by HPD chief Susan Ballard. It says, "Your medical marijuana use disqualifies you from ownership of firearms and ammunition."
Ballard points to Hawaii Revised Statutes, Section 134-7 (a), which says, "No person who is a fugitive from justice or is a person prohibited from possessing firearms or ammunition under federal law shall own, possess, or control any firearm or ammunition therefor."
On August 31, 2016, Breitbart News reported that the U.S. Court of Appeals for the Ninth Circuit ruled that a ban on gun ownership for medical marijuana users is constitutional. The decision was based on the fact that marijuana use remains illegal on the federal level, whether state-sanctioned or not. This means medical marijuana cardholders cannot pass background check form 4473 and, therefore, cannot legally purchase a firearm.
Form 4473 asks if the would-be firearm purchaser is "an unlawful user of...marijuana." No one who answers "yes" to that question can purchase a gun.