The Supreme Court has rejected another case that would have severely undermined the Affordable Care Act, also known as Obamacare.

Under Obamacare, Congress asked states to create marketplaces where people can purchase health insurance. If states refused, the federal government stepped in and created a marketplace for them. That happened in 27 states.

One aspect of the law, though, created some confusion. It seemed to indicate that people who bought insurance on the federal-run marketplaces (or exchanges as they are called under the law) would not be eligible for federal subsidies to help them pay for health insurance. This would have created a pretty big problem as it would have made health insurance unaffordable for more than 6 million people.

The president argued that this confusion was essentially a drafting error, while those opposed to the law said that Congress intentionally barred subsidies on federal marketplaces in order to incentivize states to setup their own marketplace.

In a 6-3 decision, the court sided with the president.

"Congress passed the Affordable Care Act to improve health insurance markets, not to destroy them," Chief Justice John Roberts wrote.

This is the second time that a Roberts opinion has saved Obamacare. Roberts, a conservative justice, also wrote the opinion that upheld the individual mandate, which requires all Americans to purchase health insurance.

A frustrated Justice Antonin Scalia, a conservative who has now dissented from both Obamacare rulings, joked in his dissent today that "we should start calling this law SCOTUScare."