The arrest warrant for Julian Assange should not stand and breaches "a matter of fundamental legal principle", the supreme court has heard .

Dinah Rose, Queen's Counsel, defending the WikiLeaks founder in his final appeal against extradition to Sweden to face allegations of sex crimes, told the panel of seven senior judges that to consider the Swedish public prosecutor as a judicial authority was "contrary to a basic, fundamental principle of law".

Reaching back as far into European legal history as the Codex Iustinianus, dated 376 A.D., Rose said the Swedish prosecutor was a party in the Assange case and therefore not independent and impartial, breaching the principle that "no one should be judge in their own cause", which Rose said was one of the pillars of natural justice.

Opening the case for the Swedish judicial authority, Clare Montgomery, Queen's Counsel, said the arrest warrant was valid because judicial authorities, at least in the preliminary stages of investigations where arrest is being sought, need not be independent and impartial. She said police officers made decisions to arrest people and were not considered to be independent of the prosecuting authorities. Judicial, she argued, meant simply associated with the judicial process. "The decision whether to arrest somebody might be made by somebody who is partisan," she said. "That happens throughout Europe."

She was repeatedly questioned by the judges about the reasoning behind the assertion. She ended her opening remarks by referring to historic French definitions of judicial authorities which referred to both courts and prosecutors. She will resume her case today.