AIG shares traded about 2 percent higher on the day following the news of the ruling.
Former AIG CEO Greenberg, through his company Starr International Co, sued the U.S. government in 2011, arguing the terms of the initial $85 billion loan package were unduly onerous, including an almost 80 percent U.S. stake in AIG.
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Judge Thomas Wheeler of the U.S. Court of Federal Claims ruled in favor of Greenberg on the issue of law, but Greenberg had sought as much as $50 billion in damages on behalf of Starr and about 270,000 other shareholders.
Starr International was AIG’s largest shareholder at the time of the bailout, with a 12 percent stake.