First of all, the ruling is available as a pdf on the Supreme Court's website here. The official title of the case is National Federation of Independent Business v. Sebelius (I'm not linking to the pdf directly because it sometimes causes formatting issues here).
I'm just reading the syllabus for now (the summary at the top of the opinion). Here's what I gather so far...
This part of the ruling deals with an 1867 law barring citizens from suing to stop a tax law before taxes are collected, and the court rules that the act does *not* apply to this case. Which is strange, because they go on to uphold Obamacare on the grounds that it is a legitimate use of tax power. What this means is that Obamacare is a tax for purposes of the ruling, but *not* a tax for purposes of the Anti-Injunction Act.
Because Congress describes the individual mandate as a "penalty," not a "tax," the Anti-Injunction Act does not apply.
COMMERCE CLAUSE + NECESSARY & PROPER CLAUSE
CHIEF JUSTICE ROBERTS concluded in Part III–A that the individual mandate is not a valid exercise of Congress’s power under the Commerce Clause and the Necessary and Proper Clause.
This part of the decision completely validates Randy Barnett's fairly hokey but now famous argument that, rather than regulating existing commerce, the Individual Mandate would "create commerce in order to regulate it."
The Constitution grants Congress the power to “regulate Commerce.” Art. I, §8, cl. 3 (emphasis added). The power to regulate commerce presupposes the existence of commercial activity to be regulated. This Court’s precedent reflects this understanding: As expansive as this Court’s cases construing the scope of the commerce power have been, they uniformly describe the power as reaching “activity.” E.g., United States v. Lopez, 514 U. S. 549, 560. The individual mandate, however, does not regulate existing commercial activity. It instead compels individuals to become active in commerce by purchasing a product, on the ground that their failure to do so affects interstate commerce.
Hopefully the concurrences will at least make the profound factual weaknesses of this argument plain. Indeed Congress should not be able to compel people to enter commercial activity against their will...but in point of fact the individual mandate does not do that. Instead it seeks to regulate an ubiquitous form of commerce of which all Americans are already a part, but which has been poorly construed by the law up until now. This is a failure of the court to comprehend the nature of risk pool insurance and how it differs in kind from simple exchange transactions.
As for the Necessary & Proper Clause, Roberts notes that it derives its power from enforcement of other enumerated powers, and if the Commerce Clause doesn't apply here, neither does the N&P Clause. Interestingly though, in order to make this ruling Roberts finds it necessary to invent an entirely new distinction between "necessary" and "proper" in order to disqualify the clause, implying that the Court at least recognizes the "necessity" of the individual mandate as part of a scheme to perform a legitimate function (i.e. reform interstate health insurance).
Even if the individual mandate is “necessary” to the Affordable Care Act’s other reforms, such an expansion of federal power is not a “proper” means for making those reforms effective.
Opinions are currently up in the air as to how much this part of the ruling will affect Congress' ability to expand or regulate health care & other areas of the general welfare. As I said, I personally believe the individual mandate is misconstrued in the first place, and that Congress isn't compelling anyone to enter commerce (they're compelling people to pay for commerce they are already part of).
The most straightforward reading of the individual mandate is that it commands individuals to purchase insurance. But, for the reasons explained, the Commerce Clause does not give Congress that power. It is therefore necessary to turn to the Government’s alternative argument: that the mandate may be upheld as within Congress’s power to “lay and collect Taxes.” Art. I, §8, cl. 1. In pressing its taxing power argument, the Government asks the Court to view the mandate as imposing a tax on those who do not buy that product. Because “every reasonable construction must be resorted to, in order to save a statute from unconstitutionality,” the question is whether it is “fairly possible” to interpret the mandate as imposing such a tax. [citations removed]
And the court finds that it can. By generously interpreting the plain language and the "penalty" label, and taking a generous, functional (as opposed to a skeevy, literal) interpretation of the law as written, Roberts and the majority agree with what many have said in defense of the actual law: it acts like a tax.
Neither the Affordable Care Act nor any other law attaches negative legal consequences to not buying health insurance, beyond requiring a payment to the IRS. And Congress’s choice of language— stating that individuals “shall” obtain insurance or pay a “penalty”— does not require reading §5000A as punishing unlawful conduct. It may also be read as imposing a tax on those who go without insurance.
Nor is it a capitation or poll tax, since "a tax on going without health insurance is not like a capitation or direct tax under this Court's precedents." So the tax argument stands, and the major affect of this ruling on this law (again exactly what binding precedent this will set for future laws is still very much a matter of dispute) would seem to be in the nature of kind of a semantic scolding of Congress by the Court.
This is actually a pretty big deal, I believe. Basically the ruling says that Congress exceeded its authority under the Spending Clause with its provision to revoke a state's entire Medicaid funding allotment if it refuses to go along with the Obamacare Medicaid expansion.
The threatened loss of over 10 percent of a State’s overall budget is economic dragooning that leaves the States with no real option but to acquiesce in the Medicaid expansion. The Government claims that the expansion is properly viewed as only a modification of the existing program, and that this modification is permissible because Congress reserved the “right to alter, amend, or repeal any provision” of Medicaid. §1304. But the expansion accomplishes a shift in kind, not merely degree. The original program was designed to cover medical services for particular categories of vulnerable individuals. Under the Affordable Care Act, Medicaid is transformed into a program to meet the health care needs of the entire nonelderly population with income below 133 percent of the poverty level. A State could hardly anticipate that Congress’s reservation of the right to “alter” or “amend” the Medicaid program included the power to transform it so dramatically. The Medicaid expansion thus violates the Constitution by threatening States with the loss of their existing Medicaid funding if they decline to comply with the expansion.
The gist of this ruling is that the Medicaid expansion is now going to be a whole lot more "voluntary" than before. In short, the Medicaid expansion is going to cover far fewer uninsured Americans than originally anticipated, particularly in red states hostile to the idea of social insurance to begin with. How this will shake out, given that these same individuals will instead be covered under mandatory subsidized private insurance, remains to be seen.
CONCLUSIONS (FOR NOW)
The ruling takes a somewhat ineffectual attempt to reform health care and makes it a bit more toothless. But many of the provisions of the act...mandatory coverage, no recissions, consumer rebates, subsidies, etc., remain in place, and overall this is a vindication for Obamacare and the Democrats in Congress.
Or I should say, a big semantic victory for Randy Barnett and the ridiculous broccoli clause argument, but a real, practical victory for those who see this as at least a start, albeit a flawed one, at bringing the utterly broken Frankenstein monstrosity that is the US health care system under control.