MIAMI — A Frenchman who was arrested when he arrived in the U.S. for a world beard-growing championship was sentenced Tuesday to 20 years in prison for online drug trafficking using the alias "OxyMonster." U.S. District Judge Robert Scola imposed the sentence on 36-year-old Gal Vallerius. He pleaded guilty in June to drug conspiracy and money laundering convictions.

Vallerius admitted in his guilty plea that he sold drugs himself and orchestrated other sales on an online platform for virtual currencies such as bitcoin called the Dream Market. The drugs included including cocaine, heroin, Ritalin, methamphetamine, oxycodone and fentanyl.

Investigators say Dream Market is one of the largest criminal sites for anonymous buyers and sellers to do illicit transactions. Three days before Vallerius was arrested in August 2017 arrest, authorities say there were more than 47,000 illegal drug listings on Dream Market.

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"This is a very serious offense involving a huge amount of drugs," Scola said at a hearing.

Vallerius, who sports a long brownish-red beard, was already under investigation by the U.S. Drug Enforcement Administration (DEA) when he was detained at Hartsfield-Jackson Atlanta International Airport while en route from Paris to the World Beard and Mustache Championships in Austin, Texas. He had entered the full-beard category.

Vallerius, who is from the Brittany region of France, did not speak at the hearing. His lawyer, Anthony Natale, said Vallerius is cooperating with authorities in a continuing investigation into illicit online drug transactions. That could eventually lead to a lower prison sentence, although prosecutor Juan Gonzalez said he hadn't provided enough information yet to merit such a reduction.

"He has pled guilty. He has accepted responsibility," Natale said.

Yasmin Vallerius, who is Vallerius' wife, pleaded in a letter to the judge that he show mercy on her husband. The 20-year sentence is half the maximum Vallerius could have received.

"Gal is a very caring person, very loving, and friendly with everybody," Yasmin Vallerius wrote. "He is also a very fragile and sensitive man, who is now in a foreign country far away from any family members. His arrest has broken him mentally. He has lost everything."

Undercover DEA agents made numerous purchases through Dream Market of drugs such as crystal methamphetamine, LSD and hydrocodone, according to court documents. The drugs were shipped via mail to various addresses in the Miami area.

DEA also discovered that Vallerius had Instagram and Twitter accounts. They compared the writing style of "OxyMonster" on the Dream Market forum to the writing style of Vallerius on his social media accounts.

"Agents discovered many similarities in the use of words and punctuation, including: the word "cheers," double exclamation marks, frequent use of quotation marks, and intermittent French posts," court documents say.

Agents were later able to link Vallerius to Dream Market through searches of his laptop computer and other electronic devices seized at the Atlanta airport.

Vallerius may serve some of his sentence in Great Britain, France or Israel — he is a citizen of all three nations — under an international prisoner transfer program, according to his attorney.