No one can intimate you without your cooperation (apologies to Mrs. Roosevelt for changing her quote.)
The letter informs you of a city law that is not common in the US, and tells you of the possible consequences of not following the law. Why are you intimated by that?
Many people state most firearms used in crime are stolen, using this as a reason gun control and registration is ineffective against crime. If true, and if you accept that one of the responsibilities of government is to fight crime, they should be attempting to improve their ability to track stolen guns.
Back in the 70’s Massachusetts saw a dramatic upswing is car theft, till it became the car theft capital of the country. The State responded by requiring more information to title and registrar a car, and computerizing those records. A lot of people complained about the extra paper work burden imposed on them. But the police found many cars reported as stolen were still being driven by the people who reported them stolen, after they collected the insurance money. And many other people we buying stolen cars not knowing they were stolen. The car theft rings were able to file for a new title claiming they lost the old one. The previous Dept. of Motor Vehicles poor record system was unable to detect these frauds. After a few years of the extra paper work (and good police work) car theft in Mass. fell to below the national average.
In many cities when the cops trace a firearm recovered at a crime scene back to the last person who legally brought it, that person claims it was stolen, they didn’t report it, and they don’t remember when it was stolen. A few years ago the newspaper here reported an 80 year old woman had brought about a dozen hand guns over 2 years, all of which she claimed were stolen from her, she didn’t report any of the thefts, and three of the guns were used in crimes. It is possible LA will be able to achieve a drop is gun crime with the paperwork burden they are imposing on all gun sales. Or not. But if you believe all government is unnecessary, evil, and not capable of doing anything right, you will not be happy with anything the LA city government does or does not do.