Australian Colin Russell walked free from a St. Petersburg jail on Friday, one day after being granted bail of two million rubles (US$61,500) in an appeal hearing.
Russell was the first to be brought to court when bail hearings started last week, and was denied bail at that time.
All the others were released, including Paul Ruzycki of Port Colborne, Ont., and Alexandre Paul of Montreal.
The 30 still face charges for hooliganism, which carries a sentence of up to seven years, after being arrested in September following an attempt by some of the activists to scale an offshore drilling platform belonging to state-owned natural gas giant Gazprom.
It is unclear whether the foreigners in the group will be allowed to leave Russia before the start of the trial.