London (CNN) -- WikiLeaks founder Julian Assange could end up at Guantanamo Bay if he is extradited to Sweden, his lawyers will argue next month, according to legal papers they released Tuesday.
He would be at risk of mistreatment or even execution, they will argue, saying that means Britain cannot extradite him without violating his human rights.
"There is a real risk he could be made subject to the death penalty," Assange lawyers say in documents they released Tuesday, citing British media reports that Republican politicians Sarah Palin and Mike Huckabee have called for him to be executed.
The lawyers released a preliminary outline of their planned arguments Tuesday, ahead of an extradition hearing for Assange next month.
Prosecutors in Sweden want him for questioning in connection with sexual misconduct allegations unrelated to WikiLeaks.
Assange has denied the allegations, and is free on 200,000 pounds ($310,000) bail while he fights extradition.
Assange and his lawyers appeared briefly in court in London Tuesday for a procedural hearing.
The judge in the case agreed to a change in Assange's bail conditions for two days next month so he can get to the main extradition hearing on time on February 7 and 8.
Assange is currently required by the courts to stay at the mansion of a supporter outside London every night. He'll be allowed to stay at the Frontline Club, a journalists' club in central London, on February 6 and 7 if the people who put up bail for him agree.
His lawyer Mark Stephens said that would not be a problem.
The Swedish prosecutor who issued an arrest warrant for Assange did not have the power to do so, Assange's lawyers will also argue next month.
Additionally, his lawyers will say, it's improper to issue an arrest warrant when a suspect is wanted only for questioning, not prosecution.
Prosecutor Marianne "Ny went from informal discussions about arranging an interview of Mr. Assange straight to the issuance of" a European arrest warrant without "formally summoning him for an interview or formally requesting his interrogation," they will argue.
In court Tuesday, Assange spoke only to confirm his name, date of birth and current residence in a hearing that lasted about 10 minutes.
Celebrity supporters including activist Bianca Jagger and socialite Jemima Khan were in court, and a small crowd of pro-Assange demonstrators outside held signs with slogans including "This is not 1984."
Neither Jagger nor Khan spoke to reporters before they went inside.
Assange's website, which facilitates the leaking of secret information, has released hundreds of thousands of pages of U.S. military and diplomatic documents over the past eight months.
In addition to staying at the mansion outside London, he must report to police between 2 and 5 p.m. daily, and wear an electronic tag to monitor his location.
CNN's Richard Allen Greene, Nic Robertson, Jonathan Wald and David Wilkinson contributed to this report.