A company run by former American International Group Chief Executive Maurice “Hank” Greenberg Monday filed a $25 billion lawsuit against the United States, claiming that the government takeover of the insurer was unconstitutional. In its complaint, Greenberg’s Starr International said that in bailing out AIG [AIG 21.01 — UNCH ] and taking a nearly 80 percent stake, the government failed to compensate existing shareholders. It said this violated the Fifth Amendment, which bars the taking of private property for public use without just compensation.

“The government’s actions were ostensibly designed to protect the United States economy and rescue the country’s financial system,” Starr said. “Although this might be a laudable goal, as a matter of basic law, the ends could not and did not justify the unlawful means employed.”

The United States, it went on, “is not empowered to trample shareholder and property rights even in the midst of a financial emergency.”