"A constitutional amendment may be placed on the ballot by either a two-thirds vote in the California State Legislature or by signatures equal to 8% of the votes cast in the last gubernatorial election through the exercise of the initiative power by the voters."
https://en.wikipedia.org/wiki/Constitution_of_California#:~:text=Amendments%20and%20revisions,-See%20also%3A%20California&text=A%20constitutional%20amendment%20may%20be,initiative%20power%20by%20the%20voters.