Texas and 25 other states have sued to have it shelved. The drama is sure to ensue for months, writes the Post's David Nakamura, and throw into doubt whether the fight over all of Obama's executive actions on immigration will be settled before he leaves office in January 2017.
Here's a look at other Obama agenda items that are now in the court's hands, and where they stand.
But the Supreme Court could have the final say on gay marriage's place in America when it hands down a high-profile decision in the next month on whether states that ban gay marriage violate a couple's constitutional right. The Supreme Court went Obama's way in 2013 when it allowed the federal government to recognize legally married same-sex couples.
The president's signature health-care reform law has already survived one Supreme Court challenge when in 2012, a divided court (5-4) narrowly upheld the mandate for people to have insurance by determining it was a tax.
This time around, the court is mulling another major portion of the law: Whether the federal government can subsidize health insurance for low- and middle-income people who bought their insurance on the federally run Web site, HealthCare.gov, in states that didn't set up their own exchanges. Challengers say the law as written only supports subsidies for the 16 states that set up exchanges.
Obama told U.S. Coast Guard cadets last week that failing to act on climate change will "set a course for disaster." At the same time, the Supreme Court is debating whether his method of cutting down on greenhouse gas emissions is even constitutional.
The Supreme Court heard arguments in March on whether the Environmental Protection Agency's crackdown on coal- and fire-powered plants' mercury emissions failed to consider undue costs on the power plants.
The justices are expected to share their decision in June. But it is expected to be just an early challenge to the president's executive climate change initiatives, say environmental watchers. (Sensing a theme here?)
The lawsuit against Obama's plan to shield 5 million additional undocumented immigrants from deportation isn't the only court challenge to the president's executive actions on immigration.
House Speaker John A. Boehner (R-Ohio) is considering putting to a vote a separate lawsuit against the president for expanding the program in November. This is in addition to the vote the House of Representatives took (along party lines) last summer to sue the president over his overall use of executive authority.
Neither of Congress' lawsuits has made its way to a higher court -- but with Obama's luck lately, they just might.