The campaign will need to acquire 585,000 signatures from residents of California — about 1.5 percent of the state's population — over the next 180 days. If successful, the proposition will find itself on the ballot to alter the California Constitution, notably where it describes the state as an "inseparable part of the United States" and declares the US Constitution the "supreme law of the land."
Assuming that a majority of Californians vote for the constitutional amendment, California would hold an independence referendum in 2019. If at least 50 percent of registered Californians vote, and at least 55 percent of them vote yes, then the state will secede.
Yes California argues that the United States Constitution guarantees states the right to secede on their official website. "The Constitution says that each state in the Union shall retain every power which is not by the Constitution given to the federal government," the site reads. "The Constitution does not give the power of secession to the federal government, nor does it expressly prohibit the states from exercising this power. Therefore, the power of secession is reserved to the states, or to the people, per the Tenth Amendment."
Yes California previously sought a "Calexit" in February, but withdrew the proposal after organizer Louis J. Marinelli decided to move to Russia (don't read too much into that). With their leader gone, the movement floundered and withdrew their attempt in April.
Now under new leadership, specifically the California Freedom Coalition, Yes California is trying again. Assuming that California leaves the United States, it would be the first time since the American Civil War in the 1860s that a state left the Union.
A March 2017 poll conducted by UC Berkeley found that 68 percent of Californians were against the idea of independence. However, this is an uptick from just a few years earlier: 80 percent of Californians were found to be against the idea in 2014.