NEW YORK (CNN/Money) - Billionaire investor Warren Buffett was among those whose opinions were being weighed by the nine U.S. Supreme Court justices as they heard arguments Monday regarding the McCain-Feingold campaign finance reform act.

In a special session, weeks before the court's traditional opening in October, the nine Supreme Court justices heard arguments from supporters and opponents of the law passed last year.

The high court is expected to decide, before the presidential primaries begin this winter, whether or not Congress's rewrite of campaign laws violates First Amendment free-speech protections.

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In a friend-of-the-court brief, presented and written by lawyer Steven Reiss of New York's Weil, Gotshal & Manges, Buffett said that even prominent business leaders -- those perceived to benefit the most from the access and influence purchased with soft money -- do not wish to continue funding an unrestrained campaign finance arms race.

The brief referred to a New York Times op-ed piece published Sept. 10, 2000. In the piece, Buffett quoted a fundraising senator jokingly saying to him, "Warren, contribute $10 million and you can get the colors of the American flag changed."

Supporters of the so-called McCain-Feingold law, named after Sen. John McCain, R-Ariz., and Sen. Russell Feingold, D-Wis., say it would prevent corruption in politics. But opponents counter it would criminalize free speech and the right of groups to associate with the government.