Cody Wilson -- who is currently in Taiwan according to the island's authorities -- advocates 3D-printed weapons as a bulwark against gun control, but critics warn they give criminals access to untraceable firearms.

"Detectives with the Austin Police Department Organized Crime Division filed a warrant for sexual assault for a Cody Rutledge Wilson, white male, 30 years of age," Troy Officer, the commander of the division, told journalists.

The crime is a second-degree felony punishable by up to 20 years in prison, he said.

The investigation began after a counselor to whom the victim had spoken notified police "that a juvenile female under the age of 17 had reported having sexual contact with a 30-year-old male."

The victim met Wilson on sugardaddymeet.com, a website that bills itself as the "Best Sugar Daddy Dating Site for Attractive Women and Wealthy Men Seeking Mutually Beneficial Relationships."

Wilson and the 16-year-old had sex at a hotel, and he paid her $500, said Officer.

Detectives "were able to confirm each step of the victim's story with videotape and interviews," he said.

Wilson missed a flight back to the US, and police are "working with national and international law enforcement partners to locate him and bring him to justice," Officer said.

He noted that before leaving the US, Wilson was informed by a friend of the victim that she had spoken to police.

Taiwan's National Immigration Agency said Wilson remains on the island after arriving on September 6, adding authorities have "an initial grasp of the person's whereabouts in Taiwan".

The agency said: "If the US requests judicial assistance, our relevant government agencies will follow up."

- Thousands of downloads -

Wilson published downloadable gun blueprints on his website after reaching a deal with President Donald Trump's administration in June that ended a multi-year effort by the federal government to block him.

But multiple states filed a joint lawsuit claiming Wilson endangered public safety and a federal judge issued a temporary order prohibiting the distribution of the digital blueprints.

Wilson -- who subscribes to an anarchist philosophy that the free exchange of ideas on the internet is a check on government -- then said he interpreted the ruling as only barring the free online distribution of the blueprints, and began offering the files for sale.

The recommended price per blueprint is $10, but the buyer is ultimately allowed to name the amount of money they want to pay. Many of the blueprints on the site have been downloaded thousands of times.

According to Wilson, the battle over the blueprints has ultimately aided the cause of spreading them.

"This attempt by these authorities to go into court and stifle this information drove more people to the website to download it and spread it deeper into the internet," he told AFP in August.

"No matter how badly I win or lose, you can download a gun from the internet," he said.