A few DUI checkpoint vehicles I found of note-
In this first one, note that the driver asked several times whether he was being detained, the officer refuses to answer the question- the officer would have to demonstrate probable cause to detain the person against their will, so instead he uses a very threatening demeanor. If the driver really wanted to push the issue, he could have said "Sir, if I am not being detained, I wish to continue driving. Am I being detained?"
Another checkpoint refusal that works...
Only this is the same rider, same day, wearing different gear, and getting forced to stop. Note that despite being asked, the officers refuse to give any indication of probably cause, and despite being told that he was ordered to do several things, like show ID, they refuse to acknowledge that he was stopped with an incident # (refusal to answer questions is NOT valid probably cause, only in law enforcement, it gets used that way frequently.)
Despite how I am sure I come off in this thread, I am not anti-law enforcement. I have some friends that are police officers, and I respect that they have a tough job that most officers do well. What bothers me is when people distinctly express that they wish to retain their rights, and yet their rights are still routinely ignored.