A federal judge’s ruling in a lawsuit spearheaded by former American International Group (AIG) CEO Maurice “Hank” Greenberg against the federal government sheds new light on the 2008 financial meltdown, particularly how government and the banks that caused it collaborated in its aftermath. Politically connected big banks like JPMorgan Chase & Co., Citigroup and Bank of America did just fine, while insurer AIG, itself no slouch when it came to political influence, took the fall.

AIG had two businesses: writing insurance policies around the globe for homeowners, car owners, small businesses and so on and offering a far riskier type of insurance to the crème de la crème of the world’s financial institutions. The former business was “thriving and profitable,” even in the fall of 2008, when the bursting of the housing bubble imperiled the big banks whose balance sheets were awash in subprime debt. Their claims on AIG drained the company of cash.

Had AIG declared bankruptcy, its small policyholders would have been relatively unscathed — local jurisdictions would seize assets of its various subsidiaries on their behalf. The big banks, whose transactions with AIG stood on far flimsier legal grounds, would have lost out. Enter the U.S. government, which agreed to save AIG from bankruptcy by taking it over; in exchange for an 80 percent stake in the company, the government initially loaned it $85 billion, which in turn could be paid out to the big banks bankrupting AIG. Or as Judge Thomas Wheeler put it in his opinion, “Government was able to minimize the ripple effect of an AIG failure by using AIG’s assets to make sure the counterparties were paid in full on these transactions.”

This, Wheeler ruled, was an illegal exaction.

The opinion offers a crisply told account of how AIG failed, and a fascinating section that begins on page 72 of the 75-page opinion, entitled “The Federal Government and its Agents,” that identifies in more detail the players in the American International Group bailout. Among government officials, one finds the likes of then-Treasury Secretary Henry Paulson, who joined the George W. Bush administration after a 20-year career at Goldman Sachs, and Dan Jester, who left the same firm to work as a contractor for Treasury. Chester Feldberg, the former chairman of Barclays bank, served as a trustee of the AIG credit facility. Michael Warsh, a member of the Federal Reserve’s Board of Governors, previously worked at Morgan Stanley.

Among the government’s agents was Morgan Stanley itself. The financial firm advised the Federal Reserve Bank of New York on its handling of the AIG bailout. Wachtell, Lipton, Rosen and Katz, a law firm that represented Morgan Stanley in its successful bid in September 2008 to get access to Federal Reserve support by becoming a bank holding company, concurrently provided legal advice to Treasury on AIG, including drafting the terms of a loan agreement. Goldman Sachs helped pick the government’s choice to become CEO of the insurer.

But some of the private firms acting as agents of the government in the AIG takeover had their own interest in the outcome. Barclays, Goldman Sachs and Morgan Stanley were all among the counterparties whose bad loans were draining American International Group of cash. All three benefited from the government’s seizure of AIG, collectively reaping $22.6 billion in payouts.

Which adds no small amount of injury to the insults hurled at the company. Wheeler found that, contrary to claims at the time and the testimony of some his witnesses, the insurance giant was not the “poster boy” for the risky practices that caused the meltdown. While other firms — including Goldman Sachs, Merrill Lynch and Citigroup — increased their exposure to collateralized debt obligations (like subprime residential mortgage-backed securities) right up to the beginnings of the crisis, AIG got out of the market in 2005, making it “less responsible for the crisis than other major institutions.”

Taxpayers will face no consequences from Wheeler’s decision. He found that shareholders in AIG would have lost everything had the government not intervened, so there can be no damages for the seizure. (Greenberg has vowed to appeal that part of the ruling, and the federal government might appeal in order to uphold the legality of its actions.) But they do face troubling questions about who acts in their name in the corridors of power.