A South Korean court on Monday refused an extradition request by U.S. law enforcement authorities for a man convicted of running a South Korea-based dark web child pornography site that sold videos for digital cash around the world.

The man, Son Jong-woo, operator of the website, completed an 18-month sentence for violating South Korean child protection and information laws in April but has remained in custody after he was also indicted on U.S. federal charges in Washington.

Called Welcome To Video, the website relied on the bitcoin cryptocurrency to sell access to 250,000 videos depicting child sexual abuse, authorities said, including footage of extremely young children being raped. Its upload page specifically stated, "Do not upload adult porn."

The Seoul High Court said in its ruling that it had refused the extradition request because sending him to the United States could hamper South Korean investigations into sexually exploitative content and compromise efforts to track down the users of his site for potential indictment.

Officials said last year they had arrested at least 338 people in 12 countries linked to the network, which they described as one of the largest child pornography operations they had encountered.

According to an announcement by the U.S. Justice Department last October, investigations into the site had also led to the rescue of at least 23 minors in the United States, Britain and Spain.

Son's 18-month sentence contrasted with several 15-year sentences handed out to people convicted in the United States in the case and led to efforts in South Korea to impose stricter laws and tougher penalties for child pornography offenses.

While the South Korean court said the ruling should not be interpreted as exonerating Son, and that he should actively cooperate with investigators and face proper punishment, it did not placate the enraged public, especially anti-child-pornography activists who wanted Son to be extradited.

What may have also complicated the extradition case was that Son's father opened a new legal case against his son in May in what is believed to be an attempt to foil the U.S. extradition petition.

Recent months have seen a growing revulsion against child pornography in South Korea. In May, a legal revision was made to set prison sentences for those who buy, possess, look at or watch indecent photographs or videos of children.

(With input from agencies)