The Citizens Constitutional Forum of Fiji wants the former vice president Seniloli sent back to jail.
The attorney general and minister for justice, Qoriniasi Bale, released Seniloli after only three months into his 4-year prison sentence for taking an illegal oath to become the usurper president during the coup.
Radio Fiji reports that the CCF has filed documents in the High Court applying for a judicial review of Mr Bale's decision.
The CCF's executive director, the Rev Akuila Yabaki, says if Seniloli's release is allowed to stand, then other prisoners serving time for coup related offence will also be lining up to be released on Compulsory Supervision Orders.
The Rev Yabaki says the CCF wants to ensure that Seniloli's premature release is not allowed to set a precedent.
As well, he says the CCF wants to see that the rule of law is respected in Fiji.
Seniloli held on to the office of vice president and received its salary while in prison until late November.
He resigned on his release and now collects a tax-free vice presidential pension.