the laws that cover this in the USA would be the "fair labor standards act of 1938 (flsa)" and while each state can make a law that is more gracious to the working person, the federal law is the "bottom line" of how far the laws can go to favour the employer and disadvantage the employee.

As far as I know, there are different laws for every sector like commerce, automobiles etc. Settlement of wages done accordingly. In such an agreement there are many things that should be included such as salary, wages, rules and regulations, working hours and more. You can also read about it here - convention-collective-commerce-de-gros.fr

there was follow up in the original thread, and this (in the USA) is really and truly settled law since about 1938. the thing is that the law does not go back past 3 years for recovery of lost wages and very little penalty for the employer beyond paying back wages, (so no real downside for the employer, worst that happens is they have to pay what they should have been paying anyway, and if they get away with it for 5 years between incidents where they are forced to repay, they still are ahead of the curve since they only have to pay for 3 years wages).
If I remember correctly, the "settlement" in the case in Calif. was not a trial finding of fact as much as a settlement that included 'no further discussion' by the parties and no admission of wrong doing (as usual in this sort of case). This discussion almost always gets dealer principals e-mailing each other to shut down this discussion.