NEW YORK (Reuters) - An Irish national on Friday pleaded guilty to U.S. charges that he helped run the now-defunct Silk Road, an online black market where illegal drugs and other goods were bought and sold.

Gary Davis, 30, pleaded guilty before U.S. District Judge Jesse Furman to conspiring to distribute illegal drugs. Davis said his work for Silk Road included “helping the site run smoothly” and providing customer support.

He faces up to 20 years in prison.

Davis was indicted by New York federal prosecutors in 2013, but fought extradition in Irish courts. He said he suffered from Asperger Syndrome, depression and anxiety, and argued that incarceration in the United States could hurt his mental health and endanger his life, violating his fundamental rights.

Ireland’s Supreme Court rejected those arguments, and he was extradited to the United States.

Prosecutors have said Silk Road was used in the sale of more than $200 million worth of illegal drugs and other contraband.

Silk Road was shut down in 2013 when authorities seized the website and arrested its creator, Ross Ulbricht, who was tried and convicted of drug trafficking charges, and sentenced in 2015 to life in prison.

Davis was indicted along with two others accused of working on the site. Peter Nash, an Australian, pleaded guilty and was sentenced to time served after 17 months in jail in 2015. Andrew Michael Jones, an American, also pleaded guilty but has not been sentenced.

In June, prosecutors announced the extradition from Thailand to the United States of another defendant charged in connection with Silk Road, Roger Thomas Clark. Clark, a Canadian national, has been accused of acting as Ulbricht’s “right-hand man.”