The attorney has not ruled out Russell lodging an appeal to the Court of arbitration for Sport within the allowed 21 day period.
Russell appeared to be in tears when the decision was announced at the Jamaica Conference Centre in Kingston.
The two-times Twenty20 World Cup winner was revealed to have committed the violation 11 months ago after registering three filing failures in 2015. That constitutes a failed drugs test under World Anti-Doping Agency (WADA) rules.
"Mr Russell was found guilty of a doping violation," Hugh Faulkner, chairman of the independent anti-doping tribunal that handed out the punishment, said in a statement.
The 28-year-old Jamaican, who helped the West Indies win their second World T20 title in 2016, will be banned for a year from January 31. WADA rules state that athletes across all sports must inform their local anti-doping agencies where they will be for at least one hour each day to facilitate drug tests.
A visibly upset Russell did not comment on the ruling, but his lead attorney, while disappointed his client did not beat the case, took comfort that Russell avoided a maximum two-year ban.
"Relieved it's one year, but not two years. But I genuinely thought given the circumstances and the evidence that was before the panel that he would have been exonerated," Patrick Foster told Reuters.
The attorney has not ruled out Russell lodging an appeal to the Court of arbitration for Sport within the allowed 21 day period.
"Haven't made a decision like that as yet. We have considered it but we wouldn't really consider that seriously until we have had a chance to speak with the client and look at the (written) decision," Foster said.
Russell's ban means he will miss a lucrative year of T20 cricket, including the Indian Premier League, where he plays for the Kolkata Knight Riders.
The 28-year-old Jamaican earlier this month completed a stint with the Sydney Thunder in the Australian Big Bash league.
Image: The Sydney Thunders' Andre Russell bats during a BBL match
Photograph: BBL/Twitter