The chief of the Belleville, Illinois Police Department has reportedly ordered his employees to stay out of a Denny’s restaurant there. The decision came after a group of detectives were reportedly asked by a Denny’s manager to leave the restaurant New Year’s Day.
The detectives were on-duty but not in uniform when a customer told a manager at the restaurant that at least one of the officers was carrying a gun... the manager continued to insist the detective either leave or secure the gun in her car, even after being shown badges and being told they were police.
Belleville Police Captain Don Sax said the badges were in plain view and that there were portable police radios on the table where the detectives were seated...
In the end, the officers left.
Some police agencies wisely avoid situations like this by mandating officers in plain-clothes cover their weapons by wearing jackets or something similar.
I worked plain-clothes for several years and my employer had that simple policy--if you were in public and not wearing your uniform, you were required (with some exceptions) to hide your gun and holster.
From a practical perspective, such a policy addresses the situation as a safety issue since non-uniform officers are not likely equipped with all of the usual tools of the trade, and therefore should try to avoid being readily identified.
Second, the residents of different areas of the US have varying tolerances for posessession of firearms.
In Alaska, everyone is assumed to be armed; while in Washington D.C., city laws prohibit owning and carrying guns.
Since Illinois sides with States that more actively restrict firearms, it would make sense for the chief of the Belleville (IL) Police Department to review and revise the agency's "carry" policy for non-uniformed officers--as with no jacket, the gun worn by an individual in "street clothes" may be much more visible than a badge clipped to a belt.
Wearing a jacket in Illinois in January is not too much to ask; especially in the name of officer safety and the agency's public image.