LONDON (AP) — A British judge has acquitted eight protesters who blockaded the entrance to an arms fair, accepting their argument that they acted to stop illegal weapons trading.

The defendants from Britain, Bahrain, Belgium, Chile and Peru were charged with "willful obstruction of the highway" after blocking the entrance to the huge Defense and Security Equipment International, or DSEI, trade show in London in September. They denied guilt, saying they had acted to prevent greater crimes.

Defense witnesses told the trial at London's Stratford Magistrates' Court that there was evidence weapons had been sold illegally at the fair in previous years to countries accused of human rights violations, including Bahrain and Saudi Arabia.

District Judge Angus Hamilton acquitted the defendants Friday. In a written ruling published Monday, he said the defendants were "perfectly sincere" in concluding that illegal weapons were being sold and "that their intervention was necessary to seek to prevent this."

The judge said "the court has been presented with clear, credible and largely unchallenged evidence from three experts that criminal wrongdoing had occurred at past DSEI exhibitions" and there was "a compelling inference that such activities would also take place at the 2015 DSEI exhibition."

He said police had failed to take the allegations seriously and hadn't investigated whether laws were being broken at the trade show, held every two years.