Julian Assange has moved a step closer to a US trial on espionage charges after the UK’s highest court refused to hear his appeal against extradition.

The WikiLeaks founder was attempting to appeal against a judgment by the high court in December that ruled he could be extradited after assurances from the US authorities with regard to his prison conditions there.

The supreme court said on Monday that it had refused permission to appeal “as the application didn’t raise an arguable point of law”. After the decision, the case is expected to be formally sent to Priti Patel to approve the extradition.

Assange’s lawyers will have four weeks to make submissions to the home secretary before her decision. There also remain other routes to fight his extradition, for instance by mounting a challenge on other issues of law raised at first instance that he lost on and have not yet been subject to appeal.

In January last year, district judge Vanessa Baraitser blocked extradition on the basis that procedures in prisons in the US would not prevent Assange from potentially taking his own life.

But that decision was overturned by two senior judges, Lord Burnett of Maldon, the lord chief justice, and Lord Justice Holroyde, at the high court. Burnett said the risk of Assange being held in highly restrictive US prison conditions was “excluded by the assurances which are offered. It follows that we are satisfied that, if the assurances had been before the judge, she would have answered the relevant question differently.”

Responding to the supreme court’s decision, a spokesperson for Assange’s solicitors, Birnberg Peirce, said: “We regret that the opportunity has not been taken to consider the troubling circumstances in which requesting states can provide caveated guarantees after the conclusion of a full evidential hearing. In Mr Assange’s case, the court had found that there was a real risk of prohibited treatment in the event of his onward extradition.”

City firm DLA Piper has stepped in to run an advice service for Ukrainians seeking refuge in the UK that was quickly set up by immigration lawyers following Russia’s invasion.

The website Ukraine Advice Project UK has registered over 430 volunteer lawyers and given pro bono advice in nearly 700 requests since it was set up on 28 February by lawyers Jennifer Blair, Miranda Butler, Simon Cox, Alex Piletska and John Vassiliou, supported by CJ McKinney of Free Movement.

The organisation announced last Friday that the project had grown to an ‘unmanageable’ scale for the six friends, who set up the project in their spare time. ‘We are therefore delighted to confirm that DLA Piper has agreed to provide us with desperately needed help administering volunteers and requests for advice,’ the organisation said.

‘DLA Piper’s pro bono team will draw on their experience running a similar initiative for Afghan refugees to triage and manage requests for advice and offers of assistance from volunteer lawyers.’

The website states that no information or personal data will be shared or made available to anyone in or associated with DLA Piper’s Moscow office.

Meanwhile, Hogan Lovells has told the Gazette that it has set up a joint pro bono scheme with other law firms to allow volunteer lawyers to provide basic legal information to individuals about the UK Ukrainian refugee scheme. 

Aswift ad hoc tribunal should be set up to put Vladimir Putin on trial for war crimes committed during the invasion of Ukraine, lawyers have argued.

More than 30 leading lawyers and academics from Goldsmiths University of London and other institutions have signed an open letter, seen by the Gazette, calling for urgent action to bring Putin, and those around him, to justice.

They suggest an ad hoc justice mechanism similar to those set up by the United Nations for Yugoslavia and Rwanda to prosecute those responsible for genocide, war crimes, and other atrocities and serious humanitarian violations in those conflicts.

Sir Geoffrey Nice QC, who prosecuted the former president of Yugoslavia, Slobodan Milosovic, for war crimes before the International Criminal Tribunal for the former Yugoslavia and the former Conservative attorney general, Dominic Grieve QC, have signed the letter.

Other signatories include the barristers Jessica Simor QC, Maya Sikand QC, Leslie Thomas QC and Adam Wagner, and Professor Dimitrios Giannoulopoulos, head of the law department at Goldsmiths. They call on the UK, USA and France to put political pressure on Russia to accept the authority of the International Court of Justice (IJC) and the International Criminal Court ICC).

If Russia refuses, they said, ‘the international legal order should press for an immediate and swift ad hoc justice mechanism to bring Putin, and those around him, to justice’.

They said: ‘Public realisation of the unfolding tragedy in Ukraine presents a unique opportunity to renew our commitment to international law and international human rights.’

But warned that public support may ebb once the war is over, and urged the international community to act quickly.

‘While the window is still open politicians around the globe must use public empathy with Ukraine’s plight as a driver to move the international society forward, and the Russian war machine backwards, and to ensure “never again” is not empty words,’ they wrote.

The International Criminal Court this week began an investigation into Russia’s invasion of Ukraine after 39 countries – including the UK – backed the move.