At the centre of Thursday's Supreme Court ruling is a surprising figure: Chief Justice John G. Roberts Jr., whose opinion in favour of the law elicited shock across the political spectrum.
Chief Justice Roberts, who was appointed by former president George W. Bush, was expected to vote in keeping with his conservative track record. Instead, he sided with the more liberal-leaning justices, providing a decisive fifth vote in favour of the President's health-care law.
On the right, which has long argued that the law was unconstitutional, his decision was denounced as a betrayal. For the left, it came as a welcome surprise that has prompted a re-evaluation of his reputation as a philosophical conservative when it comes to jurisprudence.
Some legal experts believe Chief Justice Roberts's decision is the result of his political evolution.
Others, however, believe the Chief Justice's underlying motive was to safeguard the integrity of the court itself in an election year. By not voting along partisan lines, they say, Chief Justice Roberts demonstrated that the court has the ability to rise above politics – exactly what it is meant to do.
"Roberts could have seen the risk to the court of deciding this controversial issue along strictly partisan lines, with the Republican appointees voting one way and the Democratic appointees voting the other," said Brad Joondeph, a constitutional law professor at Santa Clara University.
"In a sense, he saved for another day the court's capacity to reach more conservative results on other issues by buying the court a degree of political space on a highly charged issue," he added.
Bolstering Prof. Joondeph's argument is Chief Justice Roberts's speech during his confirmation, when he vowed to uphold the notion of "judicial modesty" – meaning the court should leave politics up to the politicians, which was echoed in his decision.
"We do not consider whether the [health-care act] embodies sound policies. That judgment is entrusted to the nation's elected leaders," Chief Justice Roberts wrote in the decision. "We ask only whether Congress has the power under the Constitution to enact the challenged provisions."
He decided that forcing Americans to buy insurance was unconstitutional under the Commerce Clause, but upheld the federal government's right to tax citizens who elected not to buy insurance.
Still, his vote stands in striking contrast to his past decisions. On issues such as abortion, campaign financing and affirmative action, Chief Justice Roberts has sided firmly with the court's conservative bloc.
Partisan voting, however, is one of the reasons observers say the court is viewed so negatively by the American public. A May Pew poll found that just 52 per cent of Americans currently view the court in a favourable light.
While Republicans are displeased with Chief Justice Roberts's decision on the health-care law and Democrats are unhappy with some of his past opinions, his true legacy may prove to be restoring Americans' faith in the court itself.