Stuff like this would stop if a detailed cost analysis of what Sanctuary Cities is actually costing Californians. Along with raising the comparison of how a Californian would be treated if they snuck into Mexico.
As long as it’s only affecting the regular citizens, but not the “elites” who benefit in one way or another from it while never being negatively affected, it will never stop, no matter how large a majority of regular citizens oppose it. They’re not afraid of our ballots, and we haven’t yet been pushed to wall enough to use the alternative.