TOLEDO -- A federal judge's ruling could force terrorism investigators to change their ways of choking off fundraising channels for terrorist activities.

The ruling issued last week by U.S. District Judge James Carr said the government violated the Constitution when it froze the assets of an Ohio-based charity it suspected of having ties to the militant Islamic group Hamas.

The ruling, which is likely to be appealed, could mean that the government will no longer be able to use the tactic of financially paralyzing groups it suspects are bankrolling terrorists -- unless it first gets a warrant.

Since the Sept. 11, 2001, terrorist attack, the U.S. Treasury Department has frozen the assets of seven U.S. charities and dozens of foreign organizations suspected of supporting terrorist groups.

Carr's ruling on Tuesday marked the first time a federal court has said the Treasury Department should get a judge's permission before putting a hold on an organization's funds under terror-financing laws.

"This is what safeguards innocent people from arbitrary action," said David Cole, a lawyer who assisted the charity.

"This doesn't stop the government from freezing any individual who is funding or aiding terrorism," he said. "It essentially requires the government to rewrite the rulebook."

The Treasury Department would not comment on the ruling, but a spokeswoman said it would continue to track and disrupt the flow of money to terrorist groups.

The American Civil Liberties Union says that terror-financing laws put in place by the Bush administration have given the government unchecked power over Muslim charities in the United States.

The Treasury Department in 2006 ordered U.S. banks to freeze the assets of the Toledo charity KindHearts for Charitable Humanitarian Development, saying it was funneling money to the Hamas-affiliated Holy Land Foundation and the al-Qaida-affiliated Global Relief Foundation.

KindHearts officials have denied links to any terrorist group.