Police in India's north-eastern state of Nagaland are planning to charge a British national under a special law aimed at insurgents and foreign spies.
David Ward, who is from Edinburgh, was arrested in the state last week for not possessing valid travel documents.
The authorities allege that he has close ties with Naga rebels fighting for independence from India.
The British High Commission in India says it is awaiting further clarification on Mr Ward's arrest.
Nagaland police say they will use the provisions of the National Security Act to prosecute Mr Ward.
It is generally used against people designated as enemies of the state, separatist rebels, foreign spies or major criminals.
Under its provisions anyone can be detained for at least a year without trial.
Activist
The rebels want independence from India
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Mr Ward heads a UK-based organisation, Naga Vigil, which monitors human rights violations in areas inhabited by Naga tribes.
He was first arrested in Nagaland in 1992, along with another British national, Steve Hillman, after allegedly posing as BBC journalists.
Police say they were travelling in a jeep with Naga rebels who fled when challenged at a military checkpoint, leaving behind the two British nationals.
Both were later released after former British Prime Minister John Major interceded.
Police say David Ward returned to Nagaland about two years ago and had been living with Naga rebels of the National Socialist Council of Nagaland.
He was arrested on 27 July in Noklak, 300 kilometres (185 miles) east of the state capital, Kohima.
He has since been transferred to a prison in the town of Dimapur.