Last year’s blockbuster Supreme Court employment case involved the Patient Protection and Affordable Care Act, in which the Court affirmed the Act’s constitutionality, paving the way for significant changes in virtually every employer’s health insurance policies. This year’s blockbuster case is U.S. v. Windsor, in which the Court will decide the constitutionality of the Defense of Marriage Act (DOMA). As Justice Ginsburg noted at oral argument, DOMA is implicated in more than 1,000 different federal laws.

In 1996, Congress passed and President Clinton signed DOMA, which defines marriage as the "union between one man and one woman." Its practical effect was to prohibit the federal government from recognizing same-sex marriage. DOMA’s effects in the workplace are significant. For example, it prohibits same-sex couples from the receiving the benefits of the spousal protections under the Family and Medical Leave Act as well as spousal coverage under employer-sponsored health insurance.

DOMA’s effect when enacted was modest. However, in the nearly 20 years since, the nation’s attitude toward same-sex marriage has changed dramatically. In 2004, Massachusetts became the first state to legally recognize same-sex marriage. Since then, numerous states have recognized same-sex marriage, either through legislation or judicial action.

On March 27, 2013 oral argument in Windsor was held before the Supreme Court. Edith Windsor brought this lawsuit because she was forced to pay a substantial inheritance tax on the estate of her longtime partner, which she would not have had to pay if her partner had been of the opposite sex. Ms. Windsor challenged DOMA under the United States Constitution’s Equal Protection Clause. Her attorneys argued that the right to marry was a fundamental right of each person and excluding gays from marriage violated their constitutional right to equal protection under the 14th Amendment.

It is anticipated that the Court will align along its traditional liberal and conservative lines, leaving Justice Anthony Kennedy as the swing vote. Reading the tea leaves from oral arguments, it seems likely that Justice Kennedy will join with Justices Kagan, Sotomayor, Ginsburg and Breyer in finding DOMA unconstitutional. The Court is expected to issue its decision in June of this year. Stay tuned.