Last week, I was in Prague for the third annual World Forum on Governance, which brings together people from countries around the world, including Eastern and Central Europe, Russia, China, Ukraine, Turkey, Egypt, South Africa, India, and Bolivia in search of best governing practices.

One highlight of the forum—which I codirect with Tom Mann of Brookings and Stephen Davis of Brookings and Harvard Law School—was a conversation with Pietro Grasso, president of the Italian Senate. Grasso is best known as the longtime chief of the anti-Mafia squad who survived death threats and actual assassination attempts to bring down a series of Mafia leaders and hollow out the organization. He gave a stirring talk on the international nature of corruption, but his advice to those assembled also emphasized the importance of cleaning up campaign finance.

Corruption is a cancer that afflicts societies struggling to adopt democratic values and forms of governance, and those that make no or few pretenses about democratic values. It also hits all established and venerated democracies. It can come in big forms—leaders such as Turkey's Recep Tayyip Erdogan or Russia's Vladimir Putin and their cronies, and oligarchs piling up fortunes; and it can come in smaller forms—professors in Kenya demanding sexual favors or money in return for grades, or local officials in India demanding bribes for services. It can be illegal or legal, including, as Grasso pointed out, corrupt organizations and individuals laundering their ill-gotten gains through legitimate organizations they purchase.

Laws are necessary to combat corruption, but the laws need to be enforced by honest prosecutors and judges, and they need to be bolstered by a culture that supports and abets honest governance. Both the Czech Republic and Slovakia moved to create independent judiciaries by having 12-year terms for judges, insulating them from political pressure. But the Czech Republic, thanks to Vaclav Havel, picked judges of sterling character, while Slovakia, with no Havel, picked some shady ones who now operate in a corrupt fashion, and has no ability to remove or constrain them.

Many Americans come to the World Forum on Governance, and our role, in part, has been to offer advice to reformers inside and outside governments from around the world that we would normally view as "less developed" in their democratic culture and institutions. Not this year. Lots of non-Americans knew about the U.S. Supreme Court's Citizens United and McCutcheon decisions and wondered how the United States could be slipping back so much.

That is a long introduction to get to McCutcheon. Many analysts have written a lot about the decision, with a natural focus on its direct implications for campaigns. Those are huge and important. But they are, I believe, overshadowed by the impact of the decision on corruption in America.

Here, Rick Hasen and Dahlia Lithwick, two of the best legal analysts in the country, have weighed in, and I want to add my weight.

Some have suggested that McCutcheon was not a terribly consequential decision—that it did not really end individual-contribution limits, that it was a minor adjustment post-Citizens United. Others have said that it may have a silver lining: more money to parties, more of the money disclosed. I disagree on both counts. Justice Stephen Breyer's penetrating dissent to the decision pointed out the many methods that campaigns, parties, and their lawyers would use to launder huge contributions in ways that would make a mockery of individual limits. Chief Justice John Roberts pooh-poohed them as fanciful. And, of course, they started to emerge the day after the decision.

As for disclosure, the huge amounts that will now flow in through political parties will be channeled through joint committees, state and local party committees, and others in complex ways that will make real disclosure immensely difficult, if not impossible.

More significant, in any case, were Roberts's sweeping conclusions about corruption and the appearance of corruption in the decision. The chief justice took the shaky conclusion reached by Justice Anthony Kennedy in the Citizens United decision—that money given "independently" of campaigns could not involve corruption or its appearance—and applied it in an even more comprehensive fashion to money given directly to candidates and campaigns. Thanks to McCutcheon, only quid pro quo corruption is sufficient to trigger any restrictions on campaign contributions—meaning, direct bribery of the Abscam or American Hustle variety, presumably captured on videotape for the world to see. The appearance of corruption? Forget about it. Restrictions on elected officials soliciting big money? Forget about them, too.

To anyone who has actually been around the lawmaking process or the political process more generally, this is mind-boggling. It makes legal what has for generations been illegal or at least immoral. It returns lawmaking to the kind of favor-trading bazaar that was common in the Gilded Age.

With intense competition between parties over election outcomes, with the stakes incredibly high over who will capture majorities in a polarized era, and with money everywhere and intense competition for dollars, the trade of favors for money—and the threat of damage for the failure to produce money—will be everywhere. Access to lawmakers, presidents, their aides, and subordinates is precious, including when they are actually marking up legislation. In the aftermath of Roberts's decisions, this precious access will be sold to the highest bidders.

I remember well the pre-reform era where there were "Speaker's Clubs" and "President's Clubs" with menus for soft-money donors: for $10,000, lunch with key committee chairs and a day hobnobbing with important lawmakers and committee staffers; for $25,000, all that and a small breakfast or lunch with the speaker; and so on. Those will be back, with the dollar amounts higher and the access more intimate. Big donors will make clear to party leaders that multimillion-dollar donations are one step away—and will be forthcoming if only the leaders will understand the legislative needs of the donor. McCutcheon not only made all that legal but also gave it the Supreme Court's seal of approval.

Oligarchs will rule.

Roberts has, over the past few years, taken a meat axe to 50 years and more of law and precedent on campaign finance, just as he took a meat axe to voting rights. In both areas, he showered contempt on Congress and its laws. All after he assured senators during his confirmation hearings that he would bend over backward to rule narrowly, find consensus, and respect precedent. It is hard to escape the conclusion that he deliberately misled the Senate to win confirmation.

Many of those who celebrate these decisions say they simply reflect the Constitution. Wrong.

They reflect five ideologically driven justices and their world views. If not for the decision of Sandra Day O'Connor to retire from the Court to care for her husband and his Alzheimer's disease, we would have experienced the opposite decisions in Citizens United, Shelby County, and McCutcheon. Voting rights would be protected and not suppressed, corruption would be restrained and not celebrated, oligarchs would be limited and not reigning supreme.

Ben Franklin famously answered a question about our emergent form of government following the Constitutional Convention by saying, "A Republic, if you can keep it." Thanks to Chief Justice Roberts, we have kept a republic—but it is moving rapidly toward the banana variety.