http://www.oyez.org/cases/1980-1989/1989/1989_88_1897
Michigan Dept. of State Police vs. Sitz is controlling in this case. SCOTUS held 6-3 that DUI or sobriety checkpoints are not unconstitutional if conducted within certain very specific guidelines. Whether you agree with this decision or not (I don't), it is the law of the land until SCOTUS determines otherwise.
That said, the fact that a sobriety or DUI checkpoint is presumably constitutional doesn't mean that 4A violations can't and don't occur - and here, in my opinion, that's exactly what does transpire.
There's also, in my opinion, a case to be made for tampering with evidence/obstruction of justice when the officer searching the vehicle tampers with the video camera.