Hong Kong democracy activists went to court on Thursday to challenge an emergency law that ban protesters from wearing masks, as protesters 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 embattled leader Carrie Lam had introduced a ban on people wearing masks at public rallies, colonial-era emergency legislation that has not been used in more than half a century.

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.

The legal challenger also argues 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.

Earlier this week, the Hong Kong government banned Joshua Wong, one of the most prominent faces of the pro-democracy movement in the city, from running in the upcoming district-level elections.

The protests, which have been drawing massive crowds since June following a contentious proposed extradition law that has been pulled by the government, have mutated into a movement that seeks to improve the democratic mechanisms that govern Hong Kong and safeguard – or expand – the region’s partial autonomy from Beijing.

Last week, China was planning to replace Lam as the city’s chief executive while citing people briefed on the deliberations, which would bring to a close Lam’s rule after months of pro-democracy protests.

In 2018, the Hong Kong government had disqualified the candidacy of another pro-democracy activist, Agnes Chow, for the Legislative Council by-election in March of the same year due to her stance on advocating self-determination for the former British colony.

The controversial China extradition bill was withdrawn in early September but the movement has morphed into a wider campaign for greater democracy and against alleged police brutality.

(With inputs from agency)