The Court of Final Appeal said it will hand down a decision on Monday on whether to grant leave for an appeal that seeks to ban an overseas lawyer from representing former media tycoon Jimmy Lai in his upcoming national security trial.

The Department of Justice (DoJ) has been rejected twice by the Court of Appeal in its attempts to block King's Counsel Tim Owen from defending Lai for the trial scheduled to begin on December 1.

At a hearing on Friday, the DoJ, represented by senior counsel Rimsky Yuen, said hiring an overseas counsel in the case would go against the objective of the national security law, which is to prohibit foreign forces from intervening in Hong Kong affairs.

There is also no guarantee that overseas lawyers would protect national secrets, he said.

Yuen reiterated that Owen cannot make major contributions to the case as he does not have professional knowledge of the security law here.

But Owen's counsel, Robert Pang, said the DoJ should point out if the lower courts had erred in their rulings, adding that there were no reasonably arguable grounds for an appeal.

Chief Justice Andrew Cheung noted that the lower courts had, after considering the admission criteria, stated that overseas counsel should be admitted to help with the development of jurisprudence on national security.

Justice Roberto Ribeiro, who also sits on the three-judge panel, said while Yuen is requesting a total ban on the admission of overseas lawyers in national security cases, he did not specify if special arrangements should be warranted if exceptional circumstances arise.

Lai, the founder of the now-defunct Apple Daily newspaper, faces trial for allegedly taking part in a conspiracy to print, publish, sell, offer for sale, distribute, display and/or reproduce seditious publications, as well as conspiring with others to collude with a foreign country or external elements to endanger national security.

His trial is expected to last for around 30 days.