Senior Spanish judge Baltasar Garzon went on trial Tuesday for his efforts to investigate the crimes of Francisco Franco's 1939-75 dictatorship. The trial prompted protests from international lawyers accusing Spain of weakening the universal jurisdiction on human rights by allowing the trial to proceed. Garzon, who soared to international notoriety with his attempt to extradite former Chilean dictator Augusto Pinochet in 1998, has investigated alleged human rights abuses ranging from Argentina to Western Sahara and Guantanamo. His inquiries are seen as having broken new judicial ground, especially in Latin America. But when the judge tried to launch Spain's first judicial inquiry into Franco's crimes in 2008, he met with opposition from conservative politicians and some legal experts. No members of the Franco regime were ever brought to trial for crimes committed during the 1936-39 Civil War, which brought the general to power, and the ensuing dictatorship. Spain granted an amnesty for Civil War-era crimes in 1977, two years after the dictator's death. The amnesty was seen as necessary for a divided nation to heal. But it also left Spain with tens of thousands of people buried in unmarked mass graves around the country, to the consternation of their relatives. Garzon accused Franco and 34 of his collaborators of the killings of more than 100,000 opponents during the Civil War and dictatorship. Some historians estimate the number of victims at 180,000. However, Garzon was soon forced to drop his inquiry, and was sued by two far-right groups accusing him of professional misconduct in ignoring the 1977 amnesty. The groups also accused him of overstepping his authority. The Supreme Court judge who decided to accept the lawsuit helped the groups to formulate the charges in legally acceptable language.