As state law banning motorized mining in certain areas has a clear purpose, is closely tailored, does not choose land use, and is not integrated within land use scheme, it is not field (pun?) or conflict preempted by federal mining and and use law.
Dissent: It restricts use of land.
http://cdn.ca9.uscourts.gov/datastore/opinions/2018/09/12/16-35262.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.