Three special rapporteurs issued a statement saying “Nobody should be subjected to administrative or criminal sanctions for taking part in a peaceful protest, even if the regime governing protests requires an authorisation”.

The experts said organisers of such protests shouldn’t be prosecuted for acts of violence committed by individual participants.

“Only individual acts of violence may be subject to prosecution”, they said.

The 15 suspects were rounded up last month, and include prominent, internationally-known figures like media tycoon Jimmy Lai and pro-democracy stalwarts Martin Lee and Margaret Ng.

“The persons charged are all leading figures in the pro-democracy movement. We fear the chilling effect these arrests aim to have on peaceful protests in Hong Kong,” the experts said.

The trial is due to start next Monday. The accused are facing unauthorised assembly charges under the Public Order Ordinance.

The UN experts also urged local authorities to review this law, which it says runs counter to international human rights standards because it establishes an authorisation process for assemblies.

The statement said the experts are following the cases closely, and are “in a dialogue with the relevant authorities”.