Hong Kong democracy activists went to court on Thursday to challenge an emergency law that bans protesters from wearing masks, as demonstrators vowed to use Halloween parties to defy the restrictions once more.
The international finance hub has been upended by nearly five months of huge, often violent, pro-democracy protests in which participants routinely use masks to hide their identities.
Earlier this month the city's unelected pro-Beijing leader invoked colonial-era legislation for the first time in more than fifty years to outlaw face coverings at rallies.
The move was seen as a watershed legal moment for the city since its 1997 return by Britain to China -- but the ban has done little to stop the protests or dissuade people from wearing masks.
The High Court is hearing two challenges in the same sitting. The first, from a student leader, the question's the constitutionality of the ban.
But the second challenge, lodged by some of the city's best known pro-democracy opposition lawmakers, is much broader. It aims to challenge the entire emergency law used by chief executive Carrie Lam.
"This is a duel between the rule of law and totalitarianism," lawmaker Dennis Kwok told reporters outside court on Thursday.
The sweeping 1922 emergency law was passed in a single day by then colonial master Britain to deal with striking workers and allows the city's leader to make "any regulations whatsoever" in a time of emergency or public danger.
It was last used by the British in 1967 to help suppress Maoist-backed leftist riots that raged for nearly a year and killed some 50 people.
Lam's use of the law was controversial because it bypassed the Legislative Council, the partially-elected chamber that approves Hong Kong's laws.
Critics said the move also undermined the city's reputation for being a dependable business and legal hub at a time of growing concern over Beijing's control of the city.
The legal challengers also argue it contradicts the city's more recently passed Bill of Rights which states that restrictions on core freedoms can only be justified if there is an emergency or the "life of the nation" is at stake.
When Lam announced the mask ban in early October she publicly declared that the city was not in a state of emergency.
The timing of the legal challenge coincides with the latest plan by the largely leaderless movement to defy the law.
Online forums used to organise rallies have been calling on supporters to hit the streets in masks on Thursday evening as the city celebrates Halloween.
Police told the South China Morning Post they were putting some 3,000 officers on standby as well as three water cannon trucks.
A theme park cancelled its annual Halloween party while a subway station near the city's main nightclub street was set to close at 9 pm (1300 GMT).
A police source told SCMP that officers would order revellers to "remove masks if they were chanting slogans instead of celebrating Halloween."