My sister-in-law, Faye, was aghast a few weeks ago when I told her women in America don’t get paid as much as men for the same jobs. She’s a former human rights officer in Ontario, and she declared Canadians would never put up with that kind of discrimination.

I was reminded of Faye’s incredulous reaction yesterday when groups rallied across the U.S. to support equal pay for women. They claimed women had to work until April 20 to earn as much as male colleagues who worked until Dec. 31. That’s because they figure women in this country get paid 77 cents for every dollar men earn – for the same work.

The injustice is especially glaring for women of color. Some estimates show African American women earn only 68 cents and Latinas 58 cents for every dollar that men earn.

This is even more frustrating when you consider that equal pay has been the law of the land for nearly half a century. John Kennedy signed the Equal Pay Act in 1963 and it was supposed to abolish wage disparity based on sex. But that just has not happened.

The fight for equal pay is still going on. For example, the New York State Pay Equality Coalition staged a protest in Albany Tuesday, charging that many women and people of color are still not treated fairly when it comes to wages. State Comptroller Tom DiNapoli joined the group and called for support of the state’s pending fair pay legislation.

The legislation passed a vote Monday in the state Assembly. But it’s expected to face a tough fight in the state Senate.

I am not sure why this injustice has persisted. One reason might be that in America, laws are not treated the same as they are in Canada. Canadians tend to obey laws. Americans tend to find ways to get around them. And there are often gray areas that can be exploited.

That’s especially true when it comes to work. There are numerous studies that claim to show women’s pay is not that unequal after all. One study contends that when you factor in the types of employment, and workers’ education and experience, women’s earnings rise to 81 percent of men’s … and so on.

But perhaps one study (quoted in a recent Time Magazine article) proves the women’s case beyond a reasonable doubt. This 2008 study by University of Chicago sociologist Kristen Schilt and NYU economist Matthew Wiswall examined the wage trajectories of people who underwent a sex change. Their results: even when controlling for factors like education, men who transitioned to women earned, on average, 32 percent less after the surgery. Women who became men, on the other hand, earned 1.5 percent more.

Still, clever lawyers can play games with the facts, and a heavily conservative Supreme Court seems more than willing to give them the benefit of the doubt.

For example, the male-dominated court ruled in May 2007 that women who believe they are being denied equal pay must file suit within 180 days after the discrimination occurs.

The court used this excuse to deny a lawsuit by Lilly Ledbetter  who discovered when she was nearing retirement that her male colleagues were earning much more than she was. A jury found her employer, the Goodyear Tire and Rubber Company plant in Gadsden, Alabama, guilty of pay discrimination. But in a 5-4 decision, the Supreme Court threw out the case, ruling that she should have filed her suit within 180 days of the date that Goodyear first paid her less than her peers.

While George W. Bush was president, Congress tried to pass a law that would have corrected this miscarriage of justice,  but the White House opposed the bill. With the election of Barack Obama and a Democratically controlled Congress, the new legislation was passed and signed into law last year. (Photo above shows President Obama signing the bill, accompanied by Ms. Ledbetter, back row, third from left, and a group of lawmakers.)

There’s more fair-pay legislation in the works, but I wonder how much good it will do as long as Americans are prepared to put up with the abuse and the highest court in the land is willing to perpetuate it.