Hong Kong High Court on Monday ruled out that the ban on masks is "unconstitutional", reported NHK citing the territory's media.
The directive comes as a blow to the government which is struggling to control violent protests in Hong Kong.
Early in October, Hong Kong leader Carrie Lam invoked rarely used emergency powers and banned people from wearing face masks during public assemblies. However, many protestors have defied the ban.
Meanwhile, Sunday saw stepped-up violence with protestors shooting arrows and hurling petrol bombs and bricks, while the Police fired tear gas. A Hong Kong Police Officer sustained injuries after being shot in the leg with an arrow.
The police stormed the Hong Kong Polytechnic University campus held by pro-democracy protestors, early on Monday (local time) before retreating in face of a growing fire.
The New York Times reported that "the Hong Kong Police early Monday morning tried to enter in force the university campus" that the protestors had held for several days.
Though the police were able to arrest a few protesters at the outer edges of a barricade protecting the university, they soon retreated after other students set the barricades on fire and threw dozens of petrol bombs at the police, it stated.
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