Mikael Ymer says "my conscience is clear" after being banned for 18 months for an anti-doping rule violation.
In June 2022 an independent tribunal cleared him of failing to declare his whereabouts three times in 12 months.
The International Tennis Federation then lodged an appeal with the Court of Arbitration for Sport, which imposed a ban on the 24-year-old Swede on Monday.
"I find their decision to try me again and subsequently find me guilty unfair," said the world number 51.
"On top of that, I find it difficult to comprehend that they found an 18-month suspension to be a just punishment.