The disclosure did little to shed light on who is behind the $11-million political contribution that went to a committee to oppose Proposition 30 and support Prop 32.
The group identified its donors as the Americans for Job Security and the Center to Protect Patient Rights.
Neither group is required to disclose its donors, but both have been linked to pro-business conservative groups.
Ann Ravel with the Fair Political Practices Commission says it's clear Americans for Responsible Leadership violated the law.
RAVEL: "A whole bunch of groups are just funneling money one to the other and the true source isn't known to the public and that alone is a factor that perhaps people need to know in advance of going to the polls."
ARL was preparing to take the fight against disclosure to the US Supreme Court.
The group admitted no wrongdoing, saying only that it had reached a settlement with the FPPC.