In California, most employees are employed “at will,” which means your employer can terminate you at any time, with or without a reason. They can also change your job, your pay, or discipline you, even when it may seem unfair. Employment “at will” is the default employment status in California. The exceptions to “at will” employment are: 1) if your employment contract says otherwise, which is rare, or 2) if you work for a public entity or are in a union, in which case your employer may need good cause to fire you (this would depend on what it says in your employment contract or collective bargaining agreement).
If you are an “at will” employee, your employer can terminate you without any reason at all. They do not have to give you warning, and do not need to go through any kind of progressive discipline first (i.e. a write up, demotion, performance improvement plan, etc.). An at will employee can be fired with no notice and without ever being provided a reason. While such a termination can feel surprising, unfair, and upsetting to the employee, it is not illegal.
However, here are are two exceptions where it WOULD be illegal for your employer to fire you or take an adverse employment action against you:
First, if you are being targeted for a discriminatory reason, meaning the employer fires you or disciplines you because of your race, sex, age, national origin, disability (including pregnancy), medical condition, gender identity/expression, religion, sexual orientation, marital status, veteran status, or need to take medical leave to care for your own or a family member’s medical condition. If you believe that your employer targeted you for one of these illegal reasons, you will need to have some evidence of the employer’s discriminatory motive to support your suspicion in order to successfully bring a case. One common form of evidence is a negative comment made by your employer about your protected status (as one example: complaining to you about your need for time off related to a disability). Another form of evidence is showing that your peers in a different category were treated more favorably than you. For example, in a gender discrimination case, establishing that male employees were paid and promoted at a higher rate than female employees.
Second, it may be illegal if your employer retaliates against you for making a complaint. To prove illegal retaliation under the law, you have to express a legally protected concern. A legally protected complaint would be where you expressed concern about or refused to participate in something you believed was illegal or unsafe, and you were terminated or disciplined as a result. Common examples would be where you complained about illegal discrimination based on a protected category (as described in the paragraph above), or complained about wage violations, health and safety violations or other areas where you think your employer may be violating the law. However, making a complaint that is not about something illegal (i.e. your boss micromanaging you, bullying you, or generally being horrible to you or others) is not a protected complaint and cannot be the basis for a retaliation claim. Again, you would need some evidence to link the adverse employment action to your protected complaint in order to prove that you were retaliated against.
The employee bringing the case is required to prove the reason for the termination/adverse action was illegal, what is often referred to legally as having the “burden of proof.” Having a feeling or hunch that the reason was illegal is not enough. If you can show that the reason your boss (for example) took an adverse employment action against you was because you are in a protected category (i.e. it was because of your age, race, religion etc.) or because you made a protected complaint, you may have a claim, depending on how strong the evidence is.