We need to be able to carry when we pick up our mail.
The US government began leasing / renting properties years ago. Most of your federal buildings today are not owned by the federal government.
How do they enforce a ban on guns when they don’t even own the property?
Naah. much earlier. Some uppity blacks showed up on courtroom steps in response to some white crackers (AKA CaCaLand Democrats) saying nasty things. So, within a day the bans were passed into law — so, CaCaLand no longer has open carry. And, permitted concealed carry is impossible unless you are a celebrity or politico. Or, you carry large bags of cash.
Except for the Department of Peace where employees were fully armed, according to DOGE oral report.