Why do people not understand that court cases do not make laws? California has had this law for many years (at least 2014). That service income earned from clients in CA is taxable in California. The court cases are just from someone challenging that law (and it sounds like they lost).
Here is an article from 2014 about market based sourcing:
http://www.marcumllp.com/insights-news/state-tax-update-the-shift-from-cost-of-performance-to-market...
