Vanuatu's Court of Appeal will on Friday deliver its ruling on an appeal by 14 convicted MPs against a decision to revoke their self-imposed pardons.
After being convicted of bribery last month, the speaker of parliament Marcellino Pipite pardoned himself and 13 other MPs while he was acting president.
Three of the convicted MPs, Serge Vohor, Tony Wright, and Jonas James tried to challenge Mr Lonsdale's decision in the Supreme Court, but their application was dismissed.
In the Court of Appeal on Monday, the trio's lawyer argued that the constitution only gives the president the power to pardon, but not to revoke the pardon.
But the attorney general's office, which is representing the president, argued that if the president has the power to pardon, he has the power to revoke and the fact Pipite pardoned himself was a conflict of interest.