Spencer Tripp says Paul Ruzycki of Port Colborne, Ont., one of two Canadians being held in Russia, was granted bail Tuesday.
The Primorsky court in St. Petersburg set bail at two million rubles (US$61,500) each for the nine Greenpeace activists granted bail Tuesday.
The court said they will be released if the bail is paid within the next four days. Greenpeace said it would make money available as soon as possible.
Ruzycki and Alexandre Paul of Montreal are among the activists awaiting trial for taking part in a demonstration outside a Russian oil rig back in September.
His sister, Patti Ruzycki Stirling, says she and her brother's supporters are "over the moon" to hear the news but they are still waiting to learn what his bail conditions will be.
She says they have not yet been able to speak to Ruzycki because of strict control by Russian authorities, but are looking forward to that happening soon.
"Everyone is feeling buoyed that we're moving in a positive direction and the least that we think will happen is we should be able to very quickly have a conversation with Paul and let him know how much is going on here in Canada on his behalf," she said.
Tripp says Paul, the Canadian from Montreal, is scheduled for a detention hearing on Thursday. Both Tripp and Stirling were in Toronto on Tuesday when the news about Ruzycki became known.
Bail was set for Ruzycki and eight other Greenpeace protesters from Argentina, Brazil, Finland, France, Italy, New Zealand and Poland.
One of them, Miguel Orsi of Argentina, clutched a photograph of his baby daughter and cried upon hearing the judge's decision.
Judges in Greenpeace hearings had previously agreed with prosecutors that the foreign activists in the case were a flight risk, but the Primorsky court did not say whether the seven could leave Russia while on bail.
No trial dates have been set.
Thirty people aboard a Greenpeace ship were detained in Russia's Arctic in September for a protest outside a floating oil rig and have been in custody since. The activists were initially charged with piracy, but investigators later said they were bringing hooliganism charges and that piracy would be dropped. People convicted of hooliganism are normally subject to fines, not prison sentences.
The Primorsky court refused to release an Australian activist on Monday, while another St. Petersburg court granted bail to three Russians aboard the ship, including prominent photographer Denis Sinyakov.
Nineteen other crew members are expecting court rulings on their detentions.
Former Beatle Paul McCartney had urged President Vladimir Putin to release all 30 of the detainees.