If you don't withhold CA taxes, you may be faced with fees and penalties, along with the taxes that'll be due to CA, when you file next year's tax returns. See this:
https://www.ftb.ca.gov/pay/penalties-and-interest/index.html
Remember that because of the difference in tax rates, it's unlikely that your "other state credit" for PA will totally offset your CA taxes due.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
