Gun-owning cannabis patients in Honolulu, Hawaii, aren’t feeling like they’re living in paradise right about now. After all, many recently got a letter from the Honolulu Police Department demanding they either transfer their firearms or turn them over to law enforcement.

The Honolulu Police Department has sent letters to local medical marijuana patients ordering them to “voluntarily surrender” their firearms because of their MMJ status. The letters, signed by Honolulu Police Chief Susan Ballard, inform patients that they have 30 days upon receipt of the letter to transfer ownership or turn in their firearms and ammunition to the Honolulu Police. The existence of the notices, first reported early today by Russ Belville at The Marijuana Agenda podcast, was confirmed to Leafly News this afternoon by the Honolulu Police Department. The startling order comes just three months after the state’s first medical marijuana dispensary opened in Hawaii’s capital city. The clash between state marijuana laws and federal firearms law—which prohibits all cannabis patients and consumers from purchasing firearms—is a growing point of legal contention in the 29 states with medical marijuana laws. The Honolulu letters, however, may represent the first time a law enforcement agency has proactively sought out state-registered medical marijuana patients and ordered them to surrender their guns.

The law is, unfortunately for these folks, pretty clear.

However, it does illustrate one of the primary problems with gun registration.

What? Gun registration?

Yes. Hawaii is one of the handful of states that maintain a gun registry. They know every lawfully held firearm in the state and who has it. As a result, it was easy for law enforcement to compare the two databases and figure out who owned guns and was getting medical marijuana.

While many medical marijuana advocates are upset over this, I can’t help but be curious just how many support gun registration? How many thought it would be a good idea to create a database of every gun owner in the state?

This is what happens. Gun registrations are really only useful if you want to confiscate someone’s firearms. In this case, the law may support disarming these particular individuals, but let’s face the facts. The law, as it’s being interpreted at the moment, will always support the confiscation of firearms for whatever reason.

It’s entirely possible that we’ll see more of this behavior from other departments in urban, anti-gun cities like Los Angeles or similar communities.

Either way, we can easily point to this as the reason gun registration is a problem. It doesn’t stop crime since criminals don’t register their guns. It only makes it easier for police to find who has guns so they can later take them away for whatever reason. Yes, in this case it’s using a drug that might be legal on the state level but is still recognized as illegal by federal law. What might it be tomorrow?

That’s why every gun registration scheme needs to be fought vehemently. This is the only thing they’re really effective for, after all.