The declaration of the rights of man made all french citizens equal before the law . how did this equality contrast with the way of the old regime

The Declaration of the Rights of Man abolished the three estates which had kept people unequal in the eyes of the law.

Explanation:

Under the old regime (or "Ancien Régime," to put it in French), was full of inequality.  Under the Ancien Régime, the aristocracy in France enjoyed much rank and privilege.  Being a member of the "Second Estate" (the nobility or aristocracy) meant being exempt from most taxes that supported the nation.  The 98% of the population that made up the "Third Estate" paid the costs of running a kingdom that supported the king and the aristocracy.  (Note: The "First Estate," or clergy, included high-ranking members that were essentially aristocrats, as well as low-ranking persons like parish priests who were more like commoners.)

The declaration abolished the three estates.

Explanation:

it was the first major victory for the colonists.