Your Constitution-defying state may differ. Hawaii?
A consistent, long term goal of those who wish us disarmed, is universal gun registration.
It has been pushed for, hard, several times, and been defeated.
Yes, there is a federal law against federal gun registration.
Remember, there was a federal law protecting the sanctity of marraige, as between a man and a woman, right up until there wasn't.
Creating a legal requirement to report a lost or stolen gun is part of the scheme to place gun ownership completely under the legal control of the government.