The ruling came in a lawsuit brought by the Belgian League of Human Rights, a nonprofit organization which has repeatedly called on the government to stop using ministerial decrees to implement infection-prevention measures without lawmakers' consent.
Interior Minister Annelies Verlinden said the government would appeal the ruling and that Belgium's current coronavirus restrictions, which include a night-time curfew, a ban on non-essential international travel and other measures to control infections, remain in effect.
Explaining the decision to appeal, the Interior Ministry said in a statement that the country’s highest administrative court previously ruled that “the current legal basis is indeed sufficient as a legal basis for the ministerial order.”
The court in Brussels said the Belgian state would have to pay fines of 5,000 euros per day ($5,872 per day) if it doesn't abide by the ruling within 30 days.
Prime Minister Alexander De Croo’s government has been working on a so-called pandemic law that was debated with lawmakers on Wednesday.
Belgium is among several countries that the European Union's executive commission has criticized for their restrictions on non-essential travel. The European Union said such measures could undermine the 27-member bloc's principles of free movement and trade.