They say they used it as a last resort to control a crowd that had gotten out of control.
Michigan police used tear gas to control three to four thousand unruly partyers near Michigan State University.
It all reportedly started with hundreds of people gathering to revive a tradition that had previously been shut down in the 1980s...because of uncontrollable crowds.
In this incident police say they even had to put on helmets because bottles were being thrown.
Smoke bombs and flash bangs were used before police turned to the tear gas.