Argentina’s supreme court has ruled that an American who took refuge and started a new life in the South American country can be extradited to face charges that he killed his wife more than a decade ago, a court spokeswoman confirmed on Saturday.

Kurt Sonnenfeld moved to Argentina in 2003, after prosecutors in Denver charged him with first-degree murder. The decision to extradite him brings to an end a longstanding dispute between the US Justice Department and Argentinian courts that centered in part on differences over the death penalty.

In the ruling, which was made on 11 December, the justices said US prosecutors had assured Argentina that “the death penalty will not be imposed, or if it were ruled, it will not be exercised in this case”. The ruling does not specify when the extradition may take place.

Maria Bourdin, a spokeswoman for Argentina’s supreme court, confirmed the ruling but declined to comment beyond what was in it. Calls to the US embassy in Buenos Aires seeking comment were not immediately returned.

Denver district attorney spokeswoman Lynn Kimbrough referred questions to the US Department of Justice, which said it does not comment on matters of extradition until a defendant is in the US.

Sonnenfeld was a cameraman for the Federal Emergency Management Agency (Fema) at the World Trade Center after the 11 September 2001 terrorist attacks. He claimed he had video footage indicating the government knew the attacks would happen. He also claimed that his wife, who was found dead in their home on 1 January 2002, had killed herself and that prosecutors framed him for her death to silence him, allegations that Denver’s district attorney’s office has denied.

Sonnenfeld, who published a book in Spanish about his case, El Perseguido, or The Persecuted, has a following of fellow conspiracy theorists. On a Facebook page dedicated to him, a long post in Spanish published late on Friday lamented Argentina’s decision and recounted Sonnenfeld’s claim that he was framed.

According to the page, Sonnenfeld remarried in Argentina and has twin daughters. Several private messages sent to the page on Saturday were not immediately returned.