there is fairly strong evidence that repeal of the glass-steagall act was a contributing factor to the environment that allowed investment/securities firms to get out of control in the 2001-2008 time period:
Well, what do you expect? Of the last four secretaries of the treasury, not counting the acting ones who had the job briefly, three were from Goldman Sachs. The other one was from Citicorp.
I'm pretty sure it's not possible to find congress guilty of breaking the law by using the power vested in them by the Constitution. I think the closest you could come would be laws being ratified that the Supreme court then determined (from a case being brought) that infringed on constitutional rights, in which case that portion of the law is struck, but IANAL.