The poster was put up by members of a committee representing 37 war veterans' associations from Dalmatia, who said that they met in Knin today for a convention of "truth and peace".
The committee said in a press release that they were sending "a serious warning to Croatian authorities, and particularly to all foreign blackmailers".
"No one but Croats have the right to decide in what direction Croatia will go, who they will celebrate as their hero and where a photo of any Croatian general, soldier or ordinary farmer may or may not be displayed," they said.
The committee went on to say that they "are not against European Christian association", but are "definitely against using false accusations and blackmail to prosecute our general or any other Croatian citizen".
"If you want a peaceful and safe Europe, you Europeans should help the Croatian judiciary so that our judges can prosecute events that actually happened rather than those that have been fabricated. That will help bring about positive progress in the whole region," reads the statement.