Legal Question in Investment Law in California

The answer is a definite maybe. Not all 401(k) plans are created equal, and in order to figure out whether a particular company's action in ceasing to make contributions was in violation of a contract with the employee, or more likely in violation of an Internal Revenue Code requirement, would take some study of the plan, the pattern of participation, the timing and circumstances of the company's action, and probably some other factors. As a general rule, a company is not obliged to continue its 401(k) plan for all eternity, but neither can it ordinarily just stop paying into it without jumping through hoops regarding notice period, timing, and more. A starting point for an affected employee would be to read the plan information given out by the company in the past.

The company has the right to change, stop or start different benefit plans, by following the required notice rules. They can't do anything retroactive though.