This originated (by me) as a reply to a post of someone in a similar situation. i hope you enjoy.
A couple decades back my company (~160 people) had a mandatory retreat in state, but 600 miles away. There was a mix of salaried and hourly staff required to go, I was hourly. I emailed my supervisor and HR some pointed question leading up to the weekend. Was going a condition of employment? Yes. Could I take my own transportation? No. We came to our regular work with our bags packed Friday 8AM (regular start time), would return about 10-11PM that Sunday, company was taking us to airport, then shuttle to retreat location, same for return trip. Could I visit local sites during down time? There was to be no down time, our time was scheduled down to 30 minute increments for the whole weekend. Leaving the site would be grounds for disciplinary action.
When we got back, I entered 50+ hours of overtime on my time card. Supervisor came in and yelled at me, told me to submit a new one. I refused and asked for HR. Some co-workers heard the ruckus and asked what was going on. I told them and gave my reasoning for submitting the over time. Met with HR, supervisor & director a couple hours later. They were trying to convince me that these weren't work hours, but time for self improvement. I showed them their own emails stating my employment was dependent on fully participating, and the required participation was the totality of the time there. Since I was required to be there and be actively engaged, it was 100% work time. HR wanted me to take the extra hours as compensatory time, but I declined since I had no choices regarding when the event occurred, I wanted to be fully paid for said time. The director folded his arms and said, ” Not going to happen, I'll fire you first.” I laughed and asked the HR guy to explain it to him. They stepped out for 5-10 minutes, while my supervisor harangued me about “making all this trouble.” When they got back, the HR person told me my next check would reflect the time on the condition I didnt say anything to anyone else, and produced an agreement to sign to that effect. I read it over, pushed it back and told them I cant sign it as written in good faith, as I had already discussed submitting this overtime, and the applicable laws, with about 5-6 of my coworkers already so the word was out.
Once the dust settled, that mandatory trip cost the company about $500k more in pay, legal fees and fines than they had originally budgeted for. When company leadership pushed back on other employees that submitted belated time cards, the CLWDA was notified, did an investigation that just made soup of the “policies and provisions” applied to employee overtime at that place. I voluntarily left before that company's next Annual Summit, so I don't know what if any changes were made for following years, but I'm guessing they did at the tip of the state sword.