Did that Law Enforcement officer have the right to stop me at no cause?

I was fueling up. I was transporting non-driving old order Mennonites and towing a trailer. After fueling, I went into the store. When I returned to my vehicle, a Lieutenant of the State Police was questioning the Mennonites in the vehicle. He was polite enough but I believe he had no right to do what he did next. It was a crazy busy morning rush at fuel island so he had me pull over to a less congested area of the parking lot. He then questioned me - my intentions and business, where I was coming from and going, when I had left, when I intended to return, etc. Based on all that, he told me I was in violation of the Federal Motor Carriers regulations and issued me 4 violations, but was nice enough to status them as warnings with no fines. One of the violations, however, was that I had no log book, so he placed me out of service. After he informed me of that (when giving me my copy of the violations report), he then instructed me that I had 2 options. One was to sit where I was for 10 hours. The other was to do whatever I wanted after he left. He said he was on his way to work at his office. But if I chose to leave, there was the risk of being stopped again and/or being involved in an accident or whatever. He knew I was going to leave - I had no practical choice - the Mennonites were on a schedule and needed to get back home. I made it around and back home safely and without incident. He had no way of knowing by what he said he noticed (my truck pulling a trailer) that I was doing anything wrong. I wasn't on a public roadway. I wasn't driving - the vehicle was parked at a fuel island. Etc., etc. Now I have to register with FMSCA or cease engaging in these trips for hire. I don't do them often. I report the income on my income tax, state and federal.