Members of French Polynesia's self-styled Pakumotu republic have been prevented from getting access to the assembly building in Papeete.
About 30 supporters of the group's king, Athanase Terii, said they wanted to take down the territorial flag and hoist the Pakumotu banner.
It claims that its king owns the land.
The group has been defying the French state for more than two years, refusing to recognise its authority by choosing its own president, ministers, senators and representatives.
Last year, a large police contingent acted on a court order and ended the occupation of a disused French Polynesian hospital by the same group claiming to be the rightful owners of the land.