Lord Neuberger, master of the rolls, ordered the release of documents sought by the Guardian.
Three senior judges have issued a groundbreaking judgment that strengthens the media's right to see documents used in criminal cases.
In a landmark case, Lord Neuberger, the master of the rolls, and two appeal court judges, Lord Justices Toulson and Hooper, ordered the release of documents sought by the Guardian in an extradition hearing. The US government and a magistrate had opposed disclosure of the documents.
Toulson said the decision "breaks new ground in the application of the principle of open justice". The courts should "assist rather than impede" the media when reporters sought copies of documents used in criminal cases, he said in the ruling.
The Guardian has been seeking access to documents used to justify the extradition of two Britons, Jeffrey Tesler and Wojciech Chodan, to the US. After they were sent to Texas, the pair pleaded guilty to taking part in a decade-long conspiracy to channel bribes worth $180m to Nigerian officials and politicians.
Gavin Millar, QC for the newspaper, argued that the documents would help explain why the pair were being extradited, at a time when there has been a series of controversies over the extradition of Britons to the US.
Millar said barristers in complex cases were increasingly giving written submissions to judges, to save time and costs. This meant barristers were no longer reading out the material in open court, which made it more difficult for journalists to follow cases unless barristers agreed to disclose copies of the documents.
David Perry, the QC for the US government, said the media had an established right to see documents in civil cases, but there was no such right in criminal hearings.
Toulson said the time had come for courts to acknowledge that in some cases it was necessary to give the public access to documents referred to in open court.
Toulson wrote: "In a case where documents have been placed before a judge and referred to in the course of proceedings, in my judgment the default position should be that access should be permitted on the open justice principle; and where access is sought for a proper journalistic purpose, the case for allowing it will be particularly strong."
He added: "The Guardian has a serious journalistic purpose in seeking access to the documents. It wants to be able to refer to them for the purpose of stimulating informed debate about the way in which the justice system deals with suspected international corruption and the system for extradition of British subjects to the USA."
He said the open justice principle enabled the public to "understand and scrutinise the justice system of which the courts are the administrators".
Alan Rusbridger, editor-in-chief of Guardian News & Media, said: "This is a very significant judgment in favour of open justice and should greatly strengthen the hand of journalists in being able to see documents used in criminal cases."
Toulson praised a "helpful and interesting" submission from Article 19, the human rights campaign that promotes free expression around the world. Article 19 compared Britain's access regimes with those in other countries in its submission to the court in support of the Guardian.
David Banisar, Article 19's senior legal counsel, said the judgment showed the courts were catching up with the rest of society, such as government and parliament, in opening themselves up to the public to be scrutinised and held accountable.