Tonga's Human Rights and Democracy Movement says it is confident that at least four members of the nobility will oppose controversial new constitutional changes.
The amendments, due to be debated next month by the Legislative Assembly, would tighten media controls and reduce the reach of the judiciary.
They are believed to be aimed at the Taimi O Tonga newspaper, which went back on sale last week after nearly four months of government bans.
The Democracy Movement's spokesman, Lopeti Senituli, says there were positive signs the constitutional amendment would fail when one of the Privy Council Ordinances banning the Taimi was defeated in the Assembly last week.
"There were four nobles altogther that votes against the ordinance so there is a clear indication that the nobility are not going to allow any changes to the existing basic human rights and fundamental freedoms that the people of Tonga enjoy and which were put in there by King George the 1st, the founding father of modern Tonga"
The Democracy Movement is promising a campaign of civil disobedience if the Government tries to again ban the newspaper.