The Ninth Circuit recently held, in Busk v. Integrity Staffing Solutions CITE, that the time workers spend passing through security checkpoints after work may be compensable. Security checkpoints are often used by employers who manufacture or transport goods that can be easily stolen. Two prior federal court of appeal cases ruled that time spent in security checkpoints were not compensable. The Ninth Circuit distinguished the Busk case because the checkpoints were imposed because the employer did not want to lose product to theft. In the other cases, the security checkpoint was imposed due to the nature of the work, such as working at a nuclear power facility.
I suspect that in California the time spent waiting at a security checkpoint for most reasons would be compensable. California has a different test for determining when a person is working. So long as the person is subject to the control of the employer, the time spent is time worked. Since the employee cannot leave the facility without some sort of employer-mandated search, it is easily argued that the time spent is subject to the control of the employer.
Employers should exercise caution whenever they have employees don or doff certain clothing or protective equipment, and also when they compel security checks. The time spent by the employee engaging in those activities can be considered time worked.