Papua New Guinea's Supreme Court has ruled that opposition leader Belden Namah can challenge the election of James Marape as prime minister last May.
Mr Namah's court application seeks a legal interpretation of Mr Marape's election by parliament on following the ousting of former prime minister, Peter O'Neill.
The court has been asked to interpret whether it was constitutional for Mr O'Neill to withdraw his own nomination for prime minister instead of the MP that nominated him, and for the speaker to have accepted it.
Lawyers representing Mr Marape have argued that the opposition leader's application raised issues that were not significantly constitutional.
A Supreme Court bench has ruled it was satisfied that Mr Namah has sufficient interest in the matter and that the issues he raises in the reference are serious constitutional issues.
Govt rejects Opposition claims of need for Parliament recall
Meanwhile the government rejected claims by the opposition leader that it cannot declare a State Of Emergency without recalling parliament.
The government declared a two-week SOE in response to the Covid-19 pandemic with measures including shutting down schools and non-essential businesses.
Beldan Namah had been highly critical of government's response to the coronavirus threat.
He said the SOE must be approved by parliament passing an Emergency Act to provide a legal basis for the measures.
But Police Minister Bryan Kramer said the cabinet had the power to declare a SOE, and he urged Mr Namah to study the constitution.
Health Minister Jelta Wong called on Mr Namah to stop grandstanding and work with the government to combat the virus threat.
He said this was not about government or opposition, but about fighting together to ensure PNG gets through the pandemic.