If federal dollars are being used, then definitely no. If people are using their own money, then it is a kinda gray because it could give the wrong impression to the public. Now I have gone out a couple times with 1 co-worker and I don't think it has ever been an issue. Then again, I am not sure too many people would recognize him in public or know that he is a federal employee and I am a contractor since we both are very low key. Now if they are having lunch in the employee lounge/cafeteria area and using their own money, then I don't think it is an issue. I have been invited to 1 pizza party and sat with co-workers a couple times when I ate there instead of at my desk.

Since they don't do group Happy Hour or advertise it (if they do), then I am not sure. I doubt it because of the public perception issue. I have been doing the same job since August 2009 and I don't think any issues has ever come up during that time.

As far as lunch or Happy Hour with employees at my current employer or former employer (which is actually 2 companies), I am not sure. I live less than 1 mile from HQ and I have only been inside the building 3 or 4 times since June 2017 (officially started working for them September 2017). It was the same situation with my former employer(s). Although my original former employer's HQ was in Lansdowne and my most recent former employer, who acquired the original employer 6 months after I started working on the contract, was in MD and I never stepped foot in that HQ.