State law prohibiting the formation of political committees after 30 days before an election is subject to strict scrutiny, as the law speaks to formation, a precondition for speech, and not disclosure.
The law is overbroad, as citizens might have cause to speak within the prohibited window, there are subsequent reporting requirements closer to the election, and past practice of the agency in merely imposing a $1,000 fine does not save the act.
http://media.ca8.uscourts.gov/opndir/18/06/171314P.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.