Poland has been embroiled in a long-running row with the European Union about judicial reforms which critics say increase political control over the courts. In July, a Dutch court refused to extradite a suspect in a drugs case to Poland citing doubts about the independence of judges there.
On Monday, the Warsaw District Court, accepting a request from the prosecutor, refused to extradite the couple who had fled to Poland from the Netherlands with their autistic son, who had been taken into care by the authorities.
The couple had been subject to a European Arrest Warrant, which usually ensures transfers of EU citizens, if requested, throughout the bloc, although there are some limited exceptions.
"The court paid a lot of attention ... to the issues of the independence of the Dutch judiciary and the independence of judges in the Netherlands," Deputy Justice Minister Michał Wójcik told Reuters.
"... the Dutch system is disproportionately politicised in relation to the Polish system ... in the Netherlands, politicians play a very strong role in the process of judicial appointments," he said.
The Dutch Justice Ministry could not immediately be reached for comment.
Polish state news agency PAP reported that the judge also noted that in the Netherlands euthanasia was legal after the age of 12, which could pose a threat to the boy's life.
"We are going to take our time to study this ruling," Dutch prosecution spokeswoman Martine Pilaar said. "We were not planning euthanasia for this boy, but were concerned about his wellbeing, his health and his development."
(Reporting by Alan Charlish and Alicja Ptak in Warsaw, Anthony Deutsch in Amsterdam; Editing by Alison Williams)