[UPDATE: The WSJ Law Blog rounds up reactions by the parties, while SCOTUSBlog rounds up reactions from the media and bloggers.]

[UPDATE II: For a peek behind the corporate curtain, see the memo that Republican election lawyer Benjamin L. Ginsberg (of Patton Boggs) is circulating. I think he’s going too far in his conclusions; as much as he and his clients would like corporations’ electioneering to drown out candidates’ and parties’ own communications, the disclosure requirements — which were upheld by the Court 8-1 — put a significant damper on that, since the money can still be traced to some extent, and since voters can generally discern if an ad is from a campaign or from some shadow group with an Orwellian name.]

The Citizens United v. FEC opinion has been released, with a majority opinion, two concurrences, and two concurrences-dissents, totaling 183 pages. For those of you keeping score at home:

KENNEDY, J., delivered the opinion of the Court, in which ROBERTS, C. J., and SCALIA and ALITO, JJ., joined, in which THOMAS, J., joined as to all but Part IV, and in which STEVENS, GINSBURG, BREYER, and SOTOMAYOR, JJ., joined as to Part IV.

ROBERTS, C. J., filed a concurring opinion, in which ALITO, J., joined.

SCALIA, J., filed a concurring opinion, in which ALITO, J., joined, and in which THOMAS, J., joined in part.

STEVENS, J., filed an opinion concurring in part and dissenting in part, in which GINSBURG, BREYER, and SOTOMAYOR, JJ., joined.

THOMAS, J., filed an opinion concurring in part and dissenting in part

Here’s how Justice Kennedy (joined by Scalia, Thomas, Alito and Roberts) describe the statute at issue:

The law before us is an outright ban, backed by criminal sanctions. Section 441b makes it a felony for all corporations—including nonprofit advocacy corporations—either to expressly advocate the election or defeat of candidates or to broadcast electioneering communications within 30days of a primary election and 60 days of a general election. Thus, the following acts would all be felonies under §441b: The Sierra Club runs an ad, within the crucial phase of 60 days before the general election, that exhorts the public to disapprove of a Congressman who favors logging in national forests; the National Rifle Association publishes a book urging the public to vote for the challenger because the incumbent U. S. Senator supports a handgun ban; and the American Civil Liberties Union creates a Web site telling the public to vote for a Presidential candidate in light of that candidate’s defense of free speech. These prohibitions are classic examples of censorship.

That would, indeed, be unconstitutional.

But it’s not actually the law.

Corporations, unions, and nonprofits can do all of the above, they just have to do it through a Political Action Committee. To the five conservative Justices, that, apparently, is too much:

Section 441b is a ban on corporate speech notwithstanding the fact that a PAC created by a corporation can still speak. See McConnell, 540 U. S., at 330–333 (opinion of KENNEDY, J.). A PAC is a separate association from the corporation. So the PAC exemption from §441b’s expenditure ban, §441b(b)(2), does not allow corporations to speak. Even if a PAC could somehow allow a corporation to speak—and it does not—the option to form PACs does not alleviate the First Amendment problems with §441b. PACs are burdensome alternatives; they are expensive to administer and subject to extensive regulations. For example, every PAC must appoint a treasurer, forward donations to the treasurer promptly, keep detailed records of the identities of the persons making donations, preserve receipts for three years, and file an organization statement and report changes to this information within 10 days. …

PACs have to comply with these regulations just to speak. This might explain why fewer than 2,000 of the millions of corporations in this country have PACs. … PACs, furthermore, must exist before they can speak. Given the onerous restrictions, a corporation may not be able to establish a PAC in time to make its views known regarding candidates and issues in a current campaign.

For shame. You run a multi-billion-dollar company and, before you can spend millions of dollars to influence an election, the mean old government demands you spend a couple grand on lawyers to set up a separate, regulated entity with disclosure requirements so that the public can actually know who is spending millions of dollars to influence an election.

It’s all so unfair.

Justice Stevens’ dissent (joined by Ginsburg, Breyer and Sotomayor) starts off with that malarkey: 

The real issue in this case concerns how, not if, the appellant may finance its electioneering. Citizens United is a wealthy nonprofit corporation that runs a political action committee (PAC) with millions of dollars in assets. Under the Bipartisan Campaign Reform Act of 2002 (BCRA), it could have used those assets to televise and promote Hillary: The Movie wherever and whenever it wanted to. It also could have spent unrestricted sums to broadcast Hillary at any time other than the 30 days before the last primary election. Neither Citizens United’s nor any other corporation’s speech has been “banned,” ante, at 1. All that the parties dispute is whether Citizens United had a right to use the funds in its general treasury to pay for broadcasts during the 30-day period. The notion that the First Amendment dictates an affirmative answer to that question is, in my judgment, profoundly misguided. Even more misguided is the notion that the Court must rewrite the law relating to campaign expenditures by for-profit corporations and unions to decide this case. …

Pervading the Court’s analysis is the ominous image of a “categorical ba[n]” on corporate speech. Ante, at 45. Indeed, the majority invokes the specter of a “ban” on nearly every page of its opinion. Ante, at 1, 4, 7, 10, 11, 12, 13, 16, 20, 21, 22, 23, 26, 27, 28, 29, 30, 31, 33, 35, 38, 40, 42, 45, 46, 47, 49, 54, 56. This characterization is highly misleading, and needs to be corrected.

In fact it already has been. Our cases have repeatedly pointed out that, "contrary to the [majority’s] critical assumptions,” the statutes upheld in Austin and McConnell do “not impose an absolute ban on all forms of corporate political spending.” Austin, 494 U. S., at 660; see also McConnell, 540 U. S., at 203–204; Beaumont, 539 U. S., at 162–163. For starters, both statutes provide exemptions for PACs, separate segregated funds established by a corporation for political purposes. See 2 U. S. C. §441b(b)(2)(C); Mich. Comp. Laws Ann. §169.255 (West 2005). “The ability to form and administer separate segregated funds,” we observed in McConnell, “has provided corporations and unions with a constitutionally sufficient opportunity to engage in express advocacy. That has been this Court’s unanimous view.” 540 U. S., at 203.

But what of the so-called "original meaning" of the Constitution — did the Framers intend the First Amendment’s broad language to prohibit regulatory requirements for corporate speech?

[W]hereas we have no evidence to support the notion that the Framers would have wanted corporations to have the same rights as natural persons in the electoral context, we have ample evidence to suggest that they would have been appalled by the evidence of corruption that Congress unearthed in developing BCRA and that the Court today discounts to irrelevance. It is fair to say that “[t]he Framers were obsessed with corruption,” Teachout 348, which they understood to encompass the dependency of public officeholders on private interests, see id., at 373– 374; see also Randall, 548 U. S., at 280 (STEVENS, J., dissenting). They discussed corruption “more often in the Constitutional Convention than factions, violence, or instability.” Teachout 352. When they brought our constitutional order into being, the Framers had their minds trained on a threat to republican self-government that this Court has lost sight of.

So much for "originalism."

Stevens’ conclusion puts the case in proper perspective:

In a democratic society, the longstanding consensus on the need to limit corporate campaign spending should outweigh the wooden application of judge-made rules. The majority’s rejection of this principle “elevate[s] corporations to a level of deference which has not been seen at least since the days when substantive due process was regularly used to invalidate regulatory legislation thought to unfairly impinge upon established economic interests.” Bellotti, 435 U. S., at 817, n. 13 (White, J., dissenting). At bottom, the Court’s opinion is thus a rejection of the common sense of the American people, who have recognized a need to prevent corporations from undermining self government since the founding, and who have fought against the distinctive corrupting potential of corporate electioneering since the days of Theodore Roosevelt. It is a strange time to repudiate that common sense. While American democracy is imperfect, few outside the majority of this Court would have thought its flaws included a dearth of corporate money in politics.

It’s Kennedy’s, Scalia’s, Thomas’, Alito’s and Roberts’ country; the rest of us just live in it.