In a 5-4 vote, the Supreme Court of the United States upheld the constitutionality of President Obama's signature 'Affordable Care Act' - also known as Obamacare. Chief Justice Roberts joined the majority in the decision on Obamacare.
The Affordable Care Act, including its individual mandate that virtually all Americans must buy health insurance, is therefore constitutional.
There were not five votes to uphold it on the ground that Congress could use its power to regulate commerce between the states to require every American to buy health insurance.
However, five of the justices on the court agreed that the penalty that someone must pay for refusing to buy insurance is indeed a tax that Congress can impose using its constitutionally-provided taxing powers.
Because the mandate survives, the Supreme Court did not need to decide what other parts of the statute were constitutional, except for a provision that required the 50 states to comply with new eligibility requirements for Medicaid health coverage or risk losing funding from the federal government. On that issue, the Supreme Court held that the provision is constitutional so long as states would only lose new funds if they do not comply with the new requirements, rather than all of their funding. Among the most controversial components of the law is the requirement that all institutions, except in very narrowly defined exceptions, must provide contraception (for example) even if such coverage is at odds with the values of those institutions. The Catholic bishops in the United States, among other groups, have denounced the provision as an intrusion into constitutionally provided protections of religion and the freedom of assembly.
In the majority opinion, Justice John Roberts wrote, "Nothing in our opinion precludes Congress from offering funds under the ACA to expand the availability of health care, and requiring that states accepting such funds comply with the conditions on their use. What Congress is not free to do is to penalize States that choose not to participate in that new program by taking away their existing Medicaid funding."