Secretary for Justice Paul Lam on Saturday said overseas lawyers shouldn't participate in national security cases "fundamentally", but added that the government's rules give them the chance to do so "in relevant cases."

Last year, the country's top legislature passed an interpretation of the national security law, stating that courts need approval from the Chief Executive to allow overseas lawyers without full qualifications for practising in Hong Kong to take part in such cases.

Speaking on a television programme, Lam said national security risks in the SAR could not be eliminated, and that the authorities had to manage such risks properly.

"Allowing foreign lawyers without full qualifications in the SAR to participate in cases is already an exceptional case," he said. "For cases involving national security, these lawyers shouldn't participate in such cases fundamentally."

Lam denied, however, that the government's policy meant there was an assumption to reject all foreign lawyers in national security cases.

"This is not a complete ban," he said. "We now have procedures and ways to let overseas lawyers convince the Chief Executive that they are the exceptional cases. We are giving them a chance to strive to participate in relevant cases. [The lawyers] have to prove that their participation won't pose risks on national security."

Lam added, however, that the Chief Executive would not offer explanations for rejecting overseas lawyers in specific cases.

He said disclosing the reasons would pose security risks.