Secretary for Justice Paul Lam on Saturday disagreed with claims that the role of overseas non-permanent judges has become out of date, saying having them in Hong Kong’s top court boosts the judiciary's international reputation.

Lam was speaking after Australian judge Robert French stepped down from the Court of Final Appeal last month, telling the media then that the role of non-permanent judges in the top court had become “increasingly anachronistic and arguably cosmetic”.

Speaking on a Commercial Radio programme, Lam said he’s aware that French had said he wasn’t involved in too many cases during his term at the court but that still doesn’t undermine the value of having overseas judges.

He noted it's customary to include one overseas judge in a panel of five at the top court.

“The benefit of having an overseas judge is so that the other judges can consult him in court," Lam said.

"But I have to point out why our common law system is so valuable that we even call it a 'golden brand'.

"It’s because we have a good international reputation.

“A good international reputation is a matter of quality. It’s about our judgments.

"Because court judgments are part of our legal system in common law so the content of these judgments and the laws you make greatly affect the overall level of our judiciary and our role as a leading common law jurisdiction.

"If there's participation from elsewhere, of course that will make the overall standard much better.”

Separately, when asked about how well the implementation of the national security law has been since its introduction in Hong Kong five years ago, Lam said every piece of legislation requires time and practice for continuous improvements.

The number of arrests made under the law may have been small, he said, but that's because only extremists with the intention of harming national security would be targeted.