A court in Brussels has ordered the Belgian government to lift all coronavirus containment measures within 30 days, the interior ministry says.
The government risks a 5,000-euro ($A7,713) daily fine if it does not abide by the order, which was handed down on Wednesday, several Belgian media reported.
Interior Minister Annelies Verlinden said the decision would be appealed.
The case was brought by the organisation the League of Human Rights, which argued that the legal basis for the measures had not been given and that the ministerial orders setting out the restrictions were therefore illegal.
Belgium has imposed a night-curfew and closed all non-essential shops, except by appointment, as part of its efforts to control the pandemic.
All journeys outside the country are prohibited except for essential travel such as for work or for taking care of a family member abroad.
But whether the Belgian government will follow the orders remains to be seen.
Moreover, the fine is capped at a maximum of 200,000 euros, Le Soir reported.