Q. Are my earnings liable for my spouse's debts incurred before marriage?
A. Earnings during marriage are not liable for your spouse's debt incurred
before marriage so long as these earnings when received are held in a
deposit account which is not also in your spouse's name, and as to
which they have no right to withdraw funds.
Once these monies go into the common pot, however, they become available to satisfy debts incurred prior to marriage. Family Code section 911.
Your earnings are liable for debts the other spouse incurs after the date of marriage, because the earnings are community property and debts incurred during marriage are community debts.
The only way to avoid this is by way a prenup or post-nup established before the debt is incurred (which agreement may limit or preclude the creation of community property).