Papua New Guinea's Supreme Court has ruled that a key law on political parties is against basic freedoms laid down in the constitution.
The Organic Law on the Integrity of Political Parties had been put in place in 2001 by a previous government, led by Sir Mekere Morauta, and was intended to force members to stay with the party they were elected with.
However, a challenge in the Supreme Court was upheld, with the bench finding that a member should be free to change allegiance or vote against a sitting prime minister if they no longer agreed with the party's stance.
The ruling has been welcomed by the prime minister, Sir Michael Somare.
However, he warns that the decision could send PNG back to the days when political parties were focusing on staying in office rather than focusing on develepment.
Sir Mekere, who is now the opposition leader, says the law had been abused to keep a corrupt government in power for too long.