Can states legislate their way out of gender pay differences?

Maybe California got the memo that women are the main or only breadwinners in 2 out of 5 American households.

Or maybe it’s simply the right time to start paying men and women equally for doing the same job.

For these and many other reasons, California Gov. Jerry Brown on Tuesday signed into law tough equal pay protections for women. Sen. Hannah-Beth Jackson (D) Santa Barbara, the author of the California Fair Pay Act, calls it the strongest equal pay act in the nation.

"Equal pay isn’t just the right thing for women, it’s the right thing for our economy and for California," said Senator Jackson in a statement. "Families rely on women’s income more than ever before. Because of the wage gap, our state and families are missing out on $33.6 billion dollars a year."

The fair pay law strengthens and broadens California's existing law and a 52-year-old federal law that requires employers pay men and women equally for doing the exact same job.

But now, the law requires employers to pay equally for "substantially similar work" and shifts the burden of proof to employers to justify why they provide different pay to men and women doing the same work. Employers also cannot retaliate against employees for discussing or asking how much their peers are paid.

For example: If a male chef earns more than a female chef because he works weekends, the employer would have to prove, if sued, that the weekend shifts are busier and require more work and thus account for the difference in wages, explains Jackson’s office. The restaurant would also have to show that the weekend shift was open to all chefs, and that the male chef got the job because he was the most qualified or willing to work that shift.

"The inequities that have plagued our state and have burdened women forever are slowly being resolved with this kind of bill," Governor Brown said at a ceremony on Tuesday at Rosie the Riveter National Historical Park, according to the Los Angeles Times.

The new law is supported by the California Chamber of Commerce and most state Republican lawmakers, the LA Times reports. But opponents say that it goes too far and will encourage more women to sue their employers and companies to move operations out of state.

"It is going to lead to lots more litigation, which further weakens the business climate in California," said J. Al Latham Jr., a labor lawyer and lecturer at the University of Southern California's law school.

Geoff DeBoskey, California labor lawyer to Fortune 500 companies, said the change from requiring equal pay for equal work, to equal pay for substantially similar work, is both significant and damaging to business, reports the Times.

"If an employer is going to build a new call center, they are just not going to build that in California," said Mr. DeBoskey.

Time will tell. But what’s clear now is that nationally, women who work full-time earn 82 percent of men’s salaries, according to the US Bureau of Labor Statistics. It is unclear how much of the disparity is the result of wage discrimination, and how much of it is caused by other societal trends.

In California, according to Sen. Jackson’s office, a woman working full time in 2013 made 84 cents for every dollar a man earned.

A number of other states have already passed equal pay laws, including Connecticut, Delaware, Illinois, North Dakota, and Oregon. A handful of others have pending equal pay legislation, according to the American Association of University Women.

"Women, especially women of color and mothers, continue to lose precious income to a pervasive, gender-based wage gap," said Jennifer Reisch, legal director for Equal Rights Advocates, a San Francisco-based civil rights organization. The bill signed today "will make California’s equal pay law clearer, stronger, and more effective."