“Strike” means any concerted act of more than 50 percent of the bargaining unit employees in a lawful refusal of such employees under applicable state or federal law to perform work or services for an employer, other than work stoppages based on conflicting union jurisdictions or work stoppages unauthorized by the proper union governing body.
Source:
Section 1132.6, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=LAB§ionNum=1132.6..