USPS employee refusing service?

[WhiskeyGrinder]

22. .

https://about.usps.com/postal-bulletin/2008/html/pb22228/html/info_005.html

Photography and Filming for Personal Use

Informal snapshots from handheld cameras for personal use may be allowed at the postmaster’s discretion provided that there is no disruption to Postal Service operations and that the pictures are taken from areas accessible to the public. In these cases, no prior permis­sion is required from the Office of Rights and Permissions; however, no lighting or scaffolding may be set up, and no picture can depict any Postal Service employee, customer, security camera, or cover of mail (i.e., the exterior of a mail­piece, which would show customer name and address among other things). Postmasters may restrict any and all photography if they determine that it is disruptive or there are potential security concerns.

As I say elsewhere, a person could quibble about permission vs. discretion.