In most places they are required to be locked up by law, for example in Massachusetts:

> "It shall be unlawful to store or keep any firearm in any place unless such firearm is secured in a locked container or equipped with a tamper-resistant mechanical lock or other safety device, properly engaged so as to render such firearm inoperable by any person other than the owner or other lawfully authorized user."

https://www.mass.gov/info-details/mass-general-laws-c140-ss-...