Kosovo's Constitutional Court has ruled that parliament's ratification of a border demarcation deal with Montenegro was done legally.

The court issued its decision on Monday in response to a request from opposition lawmakers, who had asked to have the Kosovo Assembly's March vote annulled on the grounds it was unconstitutional.

Opposition lawmakers used tear gas in the chamber to prevent the vote, but it nonetheless secured the minimum two-thirds support to pass.

The European Union set approval of the border deal as a precondition for Kosovo's citizens to travel without visas in Europe's Schengen travel zone.

Montenegro has approved the deal. The opposition in Kosovo claims the country loses territory under the deal, a claim denied by the government and international experts.