Cut ALL Federal funding, grants, etc. to the State of Kalifornia. Problem solved.
Secede, California, secede!
The border wall at the southern perimeter of the US may have to be modified, starting at the Colorado River, and Coast Guard boats may have to be put on Lake Tahoe.
The amputation may cause a lot of pain and bleeding at first, but like a badly decayed tooth, once removed the prognosis is much better.
CALexit is problem solved.