The Republic is the people who are served by the US Government and therefore you cannot be a US citizen and a California of the Republic citizen at the same time. California of the Republic government is not the US government, because California of the Republic is it's own nation with it's own constitution and flag. California has two constitutions, the second constitution applies to the US citizen living in the same exact boundaries that are specified by the California of the Republic constitution.
California of the Republic is: WE the people of California, greatful to Almighty God for our freedom: in order to secure its blessings, do establish this Constitution --my email address is: [email protected]