Hmmm, let's see. What do they call it when hostile foreign agents come into the boundaries of a legitimate nation and attempt to destabilize it?
Here is the deal on California.
Following the Gold Rush California was settled primarily by Midwestern and Southern farmers, miners and businessmen.
Democrats dominated the state (California) from its foundation. Southern Democrats sympathetic to secession, although a minority in the state, were a majority in Southern California and Tulare County, and were in large numbers in San Joaquin, Santa Clara, Monterey, and San Francisco counties. California was home for powerful businessmen who played a significant role in Californian politics through their control of mines, shipping, finance, and the Republican Party but were a minority party until the secession crisis.
In 1860, as tensions escalated in the East, pro-Union Californians protested the perceived pro-Southern bias of the San Francisco Roman Catholic archdiocese’s weekly newspaper, The Monitor, by dumping its presses into San Francisco Bay. In the beginning of 1861, as the secession crisis began, the secessionists in San Francisco made an attempt to separate the state and Oregon from the union, which failed. Southern California, with a majority of discontented Californios and Southern secessionists, had already voted for a separate Territorial government and formed militia units, but were kept from secession after Fort Sumter and by Federal troops drawn from the frontier forts of the District of Oregon, and District of California, (primarily Fort Tejon and Fort Mojave).
So, your portrayal of subversive southern agents being sent into California is off the mark. Like many other states, California had mixed loyalties and ambitions, including a considerable faction that wanted a totally separate country, which had nothing to do with Southern secession. And it was the North that inserted armed force into the decision making process.