Is it legal to hold someone against their will at work?

I work in fast food and work a closing shift quite regularly. When we close we are required to close, clean, and stock a certain position and once we finish that we are technically "done". Once we are "done" and the store is closed we are required to clock out, but here's the catch. We can't leave. We must sit and wait for all of the other workers and managers to finish. Because us leaving would be a "safety hazard". If we cannot leave and are required to be there against our will, should we have to clock out? Is it legal to force the workers to clock out and yet make them stay? If so, what law is this breaking, I would highly appreciate specifics.. Thanks.