By Steve Kingstone
BBC News, Madrid
The most famous case was an attempt to extradite Gen Pinochet in 1998
For more than a decade, a drab, beige building in central Madrid has been the global destination of choice for anyone wanting to file allegations of genocide, torture and crimes against humanity.
The Audiencia Nacional - National Criminal Court - has heard complaints of human-rights abuses as far afield as Guatemala, Rwanda, Chile, Tibet, Gaza and Guantanamo Bay.
Currently, 10 cases from five continents are being investigated by Spanish judges, under the principle of "universal jurisdiction," which holds that some crimes are so grave that they can be tried anywhere, regardless of where the offences were committed.
In a recent statement, almost 100 organisations collectively praised Spain's "pioneering approach," gushing that the country "should feel proud of itself" for becoming a reference point for other nations.
Except, Spain's left-leaning government sees things rather differently.
In parliament, it is sponsoring a controversial change in the law, which would limit the future scope of universal jurisdiction to cases in which (i) the victims are Spanish, (ii) the alleged perpetrators are in Spain, or (iii) some other clear link to Spain can be demonstrated.
On Thursday, the proposal was approved by lawmakers in the lower house by an overwhelming 341-2 vote, with three abstentions. Senate approval is seen as a formality.
'Enormous backwards step'
"Universal jurisdiction doesn't necessarily work," argues Angel Lossada, Secretary of State for Foreign Affairs, explaining the government's policy.
Ms Gonzalez Vera says "the Pinochet case was triumph of justice"
"Without a connection to Spain, it presents problems of obtaining proof and co-operation from other states. And then the cases do not conclude."
He has a point. All too often, inquiries by the Audiencia Nacional have produced complex legal arguments with the states concerned, filling pages of court documents but rarely the dock.
Only Rodolfo Scilingo, an Argentine former naval officer, has been convicted in Spain under universal jurisdiction - although the court's defenders point out that a second Argentine, Ricardo Cavallo, was extradited from Spain to face trial back home.
The government's approach has appalled campaigners who argue that, with or without convictions, the Audiencia Nacional has commendably shed light on dark acts committed by closed regimes.
The campaigners include witnesses from the most famous case of all - the attempt by Judge Baltasar Garzon to extradite Chile's Augusto Pinochet on murder charges in 1998.
"For me, the Pinochet case was a triumph of justice - together with Nuremberg, it was the most important international prosecution of the past 100 years," explains Laura Gonzalez Vera, whose husband was murdered by the general's secret police.
"In Chile, the killers are still protected by an amnesty law, but the investigation in Spain destroyed Pinochet politically."
Mr Guzman is deeply critical of the government's plan to change the law
Another key witness, Oscar Soto Guzman, was the personal physician of Salvador Allende, the elected left-wing president who committed suicide when Pinochet's troops stormed his official residence in September 1973.
The doctor is deeply critical of the government's plan to change the law.
"It's a move which completely contradicts everything that's happened up until now," he says.
"We went legitimately through the Spanish courts to take the Pinochet case forward, but this is an enormous backwards step."
In common with the human rights lobby, Mr Guzman accuses the politicians of acting out of political motives.
"For the government of the day, I suppose it's more comfortable to forget the past and avoid diplomatic problems. There have been very strong international pressures in these cases - above all, from Israel."
Israel's intervention, in January, followed the opening of an inquiry by the Audiencia Nacional into a bombing raid on Gaza in 2002, which targeted a known Palestinian militant but also killed 14 civilians.
Seven Israelis - a mix of politicians, officials and military officers - were accused of crimes against humanity.
In a statement, the Israeli government branded the inquiry in Madrid "unacceptable," while the then Foreign Minister Tzipi Livni told her Spanish counterpart the killings were already under investigation in Israel.
Soon afterwards, Madrid confirmed that the law on universal jurisdiction would be changed.
"The Spanish foreign minister was scared," alleges Gonzalo Boye, the lawyer who filed the complaint against Israel.
"This is the wrong concept of foreign relations. Instead of dealing as equals, they are dealing from a position of submission to countries which are protecting war criminals."
Mr Boye claims that ongoing cases against China (Tibet) and lawyers for the Bush administration (Guantanamo Bay) added to the government's desire to put a stop to such diplomatically-sensitive probes in future.
But the foreign ministry strongly denies caving in to the concerns of heavyweight governments.
"This is not about pressure from one country or another, but rather it's about deciding the best role for Spain in tackling impunity," insists Mr Lossada.
Pointing out that the current Spanish rules predate the International Criminal Court (ICC) and regional tribunals, Mr Lossada argues that "today, there are a lot of international instruments that are more efficient and more consensual" than pursuing such cases in Madrid.
However, the ICC can only prosecute cases dating from after its inception in 2002.
Whatever its motives, the government has won quiet praise from some of the countries directly affected.
"This change will be helpful to the Spanish government," says Irit Kohn, a veteran Israeli lawyer. "It will have a filter effect, and provide restraint in cases which are politically motivated."
An official from another influential nation agrees that the move is "understandable", likening sensitive cases at the Audiencia Nacional "to an 800lb gorilla in the room" of bilateral relations.
The new law is not expected to be retroactive - meaning that high-profile existing cases will continue.
But nonetheless, human-rights groups were quick to denounce Thursday's parliamentary vote as a cynical ploy by politicians to rein in Spain's crusading judiciary.
In a statement, Amnesty International wrote: "A clear message has been sent out, that Spain is more concerned with not offending certain powerful governments than with ending the impunity enjoyed by criminals."