The opposition leader in Papua New Guinea, Sir Mekere Morauta, says the time is right for the rule of the prime minister, Sir Michael Somare, to come to an end.
The comment comes after the Supreme Court ruled that the Organic Law on the Integrity of Political Parties violated some basic democratic principles.
The law had been put in place by Sir Mekere's government nine years ago but he now says the law had been abused to keep a corrupt government in power for too long.
Sir Michael has also welcomed the ruling, but warned that it could send PNG back to the days when political parties were focusing on staying in office only.
Our correspondent, Jonathan Tannos, says the law had imposed stable government.
"This was the stability that has always been insisted upon by major investors and they really needed such a guarantee in order to spend money in Papua New Guinea."