You can't sue. You can report it to the DOL and OSHA if any OSHA regulations were also violated (that part isn't clear), but those agencies would investigate and determine if any sanctions are warranted. IF this was part of a co-op program, it is entirely possible your employer had a waiver to allow you to do the work that you did as it was part of your training. This is very common otherwise many vocational programs would not exist.