Glavas is suspected of war crimes against Serb civilians committed in the eastern city of Osijek in 1991.
Court spokesman Kresimir Devcic said the State Prosecutor's Office could appeal Posavec's decision within 48 hours, with the deadline beginning on Monday.
The State Prosecutor's Office said on its website Posavec once again rejected their request with the explanation that the prosecution did not present significant new circumstances which would warrant taking Glavas into custody. The Office said it would appeal the investigating judge's decision.
In the second detention request submitted yesterday, the Office said that an Osijek County Police report provided grounds to suspect concrete influence on witnesses as well as new facts and evidence which were not considered when detention had been requested the first time.