A US court has struck down part of the Bush administration's controversial anti-terror Patriot Act.
Bush defended the act in his State of the Union address
Judge Audrey Collins ruled that the law's ban on giving "expert advice or assistance" to terrorist groups was too broad and limited free speech.
It is the first time a federal court has struck down any part of the law, which was passed in the wake of the 11 September 2001 attacks on the US.
The Justice Department said it would review the decision before responding.
Humanitarian groups that work with Kurds in Turkey and Tamils in Sri Lanka had sued the US Government over the law.
They argued that the Patriot Act was so vague that activists had been afraid to organise conferences or publish political material for fear of violating it.
Judge Collins agreed, writing in her decision that the Patriot Act "could be construed to include unequivocally pure speech and advocacy protected by the First Amendment" to the US Constitution.
The ruling came shortly after President George W Bush defended the Patriot Act in his annual State of the Uinon address.
Ashcroft crossed the country in support of the Patriot Act
In his speech, he urged Congress to make permanent parts of the law that are due to expire automatically in 2005.
There has been increasing uneasiness about the law since it was passed in late 2001, with critics arguing that it grants the government too many sweeping powers.
Attorney General John Ashcroft, the country's top law-enforcement officer, toured the US to drum up support for the law last year.
Responding to Judge Collins's ruling, the Justice Department called the Patriot Act "an essential tool in the war on terror".
"By targeting those who provide material support by providing 'expert advice or assistance', the law made clear that Americans are threatened as much by the person who teaches a terrorist to build a bomb as the one who pushes the button," spokesman Mark Corallo said.
A number of aspects of the Bush administration's anti-terror policy have come under attack in the courts, including the designation of people as "enemy combatants" - who are not entitled to legal safeguards.
The US Supreme Court has agreed to consider whether US courts have jurisdiction over people in this category being held outside of US territory at Guantanamo Bay, Cuba.