Sax said the manager responded stating that company policy stated that only officers in uniform may have weapons. Rice went on to state there was a sign on the door indicating weapons were only allowed in the restaurant if officers were in uniform.So that point seems to be in dispute. Regardless, the restaurant has the right to ask a customer to leave if they feel that customer is making other customers uncomfortable.
[later in the story:]
Sax said there was no sign posted on the door of the restaurant stating police officers must be in uniform if they have a weapon.
Of course a restaurant has the right (or should have) to ask a customer to leave if that customer makes other people feel uncomfortable. In this case an anti-gun person would ask the armed person to leave and a gun supporter would ask the anti-gun person to leave. Which would you ask to leave?