A dispute over the dismissal of dozens of workers from the Marciano Art Foundation widened on Monday as lawyers representing a former employee accused the organization of breaking a state law that requires notice before mass layoffs.

About 70 people working at the foundation, a private, nonprofit museum in Los Angeles, were laid off in November, days after taking steps to form a union. At the same time, the foundation, which was created by two brothers who co-founded the Guess clothing empire, told those employees in an email that it would close its current exhibition early, citing “low attendance the past few weeks.”

Lawyers representing one of the laid-off workers, Kenneth Moffitt, filed a suit that they said was accepted Monday by the California Superior Court in Los Angeles. That complaint asserted that the foundation and the brothers, Paul and Maurice Marciano, had violated a law that requires certain employers to provide employees and government officials at least 60 days written notice before ordering a mass layoff, relocation or cessation of operations.

The suit asked to be certified as a class action and for the former employees to be awarded damages of at least 60 days back pay and the value of lost benefits. It also asked for an injunction forbidding the defendants from engaging in unlawful practices.