When workplace conditions become so bad that any reasonable person would feel compelled to quit, the law will sometimes treat that person as if they were fired instead.
This can open the door up to a claim of constructive dismissal (also called constructive discharge), which is a type of wrongful termination claim.
This type of claim rests on the idea that an employer can sometimes be so manipulative that an employee is forced into resigning. Since California is an at-will state where employers are generally free to hire and fire whom they please unless it's for a reason that's discriminatory or otherwise against public policy, the purpose behind the employer's actions is usually to get around that single pesky issue—which makes it illegal.
For example, if an employer wants to get rid of employees over the age of 40 so that he or she can replace them with younger, less well-paid workers, it would be illegal to just fire them—employees over the age of 40 are part of a federally protected class and can't be discriminated against based on their age. Instead, the employer may try to make working conditions so horrible just for those older employees that they feel compelled to quit.
It's important to keep in mind that your employer's conduct can't just be merely bad in order to give rise to a successful claim—the conduct has to be exceptionally intolerable and give you no other real choice but to quit.
In California, you also have to prove that your employer intended to force your resignation or had actual knowledge that the conditions were intolerable. That usually means that you have to at least address the issue with your employer or someone high enough in authority that you give the company a chance to correct the situation.
It's also difficult to prove a constructive discharge based on a single event—unless that event is somehow so extreme that it alone creates intolerable working conditions. For example, if the foreman on your construction job threatened you with a crowbar and you walked off the site, that could constitute a constructive dismissal.
If you believe that your employer essentially forced you into quitting your job in order to skirt the law, contact a wrongful termination attorney to discuss the possibility of a case.
Source: FindLaw, "Constructive Dismissal and Wrongful Terminations," accessed March 03, 2017