what is california law pertaining to mandatory overtime?

Answer 1

the only time it is mandatory is is if you want to keep your job, the empoyer can require you to work it as part of the job. the employer may discipline an employee, up to and including termination for not doing it.
there is no legal obligation to work it.
the law for pay, if you are not a salaried employee is this
One and one-half times the employee's regular rate or pay for all hours worked in excess of eight hours up to and including 12 hours in any workday, and for the first eight hours worked on the seventh consecutive day of work in a workweek; and
Double the employee's regular rate or pay for all hours worked in excess of 12 hours in any workday and for all hours worked in excess of eight on the seventh consecutive day of work in a workweek.
A salaried employee must be paid overtime unless they meet the test for exempt status as defined by federal and state laws, or unless they are specifically exempted from overtime by the provisions of one of the Industrial Welfare Commission Wage Orders regulating wages, hours and working conditions.

Answer 2

there is no mandatory overtime law, there is a law though that states if you work overtime your employer should pay you time and a half. if your boss says its mandatory that's bullshit!