A Kenyan court has lifted a ban on a group demanding an independent state around the coastal city of Mombasa - a popular tourist destination.
The government outlawed the Mombasa Republican Council (MRC) in 2010, describing it as a "criminal group".
The government has said it will appeal the High Court's ruling that the ban was unconstitutional.
The ruling raises concern that Kenya's stability could be threatened by louder calls for secession, analysts say.
The MRC accuses the government of marginalising the indigenous ethnic groups living along the coast, which is also the centre of the country's tourism sector.
Dozens of MRC members have been arrested this year as the security forces try to enforce the ban.
The court said there was no evidence that the MRC had engaged in criminal activity.
"The court has been able to deduce that MRC is a political movement. Secession is a political agenda," Justice Francis Tuiyot said.
"The court therefore grants the MRC a chance to enjoy their political right. They should organise and register as a political party."
The court, however, stressed that the MRC must campaign for independence in a democratic way, without inciting war or promoting hate speech.
The MRC applauded the decision and the possibility of holding talks with the government.
Attorney General Githu Muigai said the government would appeal against the decision.
"Any group or organisation challenging the constitutional authority and territorial integrity of the Republic of Kenya cannot enjoy protection by the constitution," he said.
The acting head of Kenya's Civil Service, Francis Kimemia, said security chiefs would hold an emergency meeting on Thursday to discuss the "grave implications" of the ruling.
"The rule of law will continue to be enforced without fear or favour," Mr Kimemia said.
"The government assures Kenyans of their security and that of their property countrywide."
In the past the government has rejected talks with the MRC, saying it must first drop its demands for independence.
The BBC's Kevin Mwachiro in the capital, Nairobi, says, the issue of secession of the coastal region, is not new and seems to resurface in the run-up to a general election.
Kenya is due to go to the polls again in March next year.