A court in Uganda has ruled as unconstitutional a law which prevents political parties from carrying out their activities.
Museveni may be forced to change
Under the law passed last year, parties are not allowed to hold rallies, take part in elections or have offices outside the capital, Kampala.
But the court on Friday agreed with the petitioners who had insisted that the law is "unjustifiable, non functional and inoperative".
The court also agreed that the act, known as the Political Organisations Act 2002, effectively makes Uganda a one-party state in favour of the government sponsored system of government.
Since coming to power in 1986, President Museveni has refused to allow parties to operate, ruling through a non-party political system known as the " Movement".
One of the petitioners, Dr Paul Ssemogerere, a leader of an unregistered political party, said the unanimous court judgement "safeguards inherent freedoms that have been curtailed for years".
"According to the judgement, the Movement is now treated as a political party that cannot enjoy preferential treatment," he added.
A lawyer representing the petitioners described the ruling as a landmark in the history of Uganda.
He told the BBC's Will Ross in Kampala that he had already advised political parties to begin organising themselves to hold activities like conferences and rallies.
Friday's ruling comes ahead of a meeting of the Movement's senior officials, called by President Museveni for next week.
Our correspondent says this meeting is likely to determine the future political landscape in Uganda.
In February, the press reported Mr Museveni declaring himself in favour of returning the country to a multiparty political system.