The attorney for Viktor Bout, a convicted Russian arms trafficker for whom WNBA player Brittney Griner and former Marine Paul Whelan could be traded, told CNN on Monday he’s “confident” the swap will get done, based on information from “the Russian side.”

“Look, it’s no secret they’ve been wanting him back for several years now. They’ve been trying to get him back for decades,” Steve Zissou said.

Griner is on trial in Russia after being arrested in Moscow in February when officials found cannabis oil in her luggage. Whelan was detained in December 2018 on espionage charges.