The Osaka High Court on Wednesday overturned a lower court decision and acquitted a tattooist for operating without a medical license, ruling the process is not a medical practice.

"The tattooing procedure is not relevant to medicine and it does not constitute a medical act controlled under the medical practitioners' law," said presiding Judge Masaki Nishida in handing down the ruling on tattoo artist Taiki Masuda's case.

In September last year, the Osaka District Court ruled Masuda had performed unlicensed medical procedures when he tattooed the arms and other body parts of three women between July 2014 and March 2015 at his home and studio in Suita, Osaka Prefecture. Masuda was ordered to pay a fine of ¥150,000.

The district court reasoned "the treatment could possibly cause skin lesions or allergies" so tattoo artists need medical knowledge and expertise to understand the risks and how to properly deal with any complications.

The case initially went to trial after Masuda refused to pay an initial fine of ¥300,000 under a simplified criminal proceeding called a summary indictment in August 2015.