Legality Of Supervised Urinalysis

I have been staying at a not for profit transitional housing facility through the VA for the past four months. The staff are not medically trained, with th le exception that they administer pills to clients with prescriptions. We are free to come and go as we please, as long as we are back before 11pm. If we show up later than that, we are required to take a breathalyzer, and have our vitals measured and recorded. We are also required to take a urinalysis. There are no repercussions if the results are positive, as this is not a rehab facility. The primary purpose of the program is to remove barriers to housing. During my time here, i have taken st least 20 urinalysis tests that have always been negative. The process has been the same for everyone across the board the entire time. They hand you the cup, you take it to the bathroom by yourself, and you bring it back to the office when you are finished. You then pull the label off to reveal the results, which are then recorded on a paper with the rest of your vitals, you sign it, then they give the cup back to you to go dump out and you carry on with your day.

Upon returning this last time, I went in to the office and was told that the director wanted them to start watching us pee now, so they had to watch me.Initially, ,I couldn't pee and they left me alone for about 15 minutes until they called me back into the office. One of the workers started to interrogate me and ask me if I had any kidney issues or anything. I told her no and she said that my body produces 30ml of urine per hour, so I had pee in my bladder. She was basically calling me a liar. After standing in the bathroom supervised for a other 20 minutes, I was finally allowed able to pee and the test came back negative. Since then, it appears as though I am the only person that has been supervised. I feel like my privacy has been violated and I feel humiliated by the staff and singled out for no apparent reason. I just want to know if they have any legal authority to supervise me again the next time I have to take one.