The Nepal authorities should immediately withdraw sedition charges and unconditionally release rights campaigner Chandra Kant Raut, Human Rights Watch said Tuesday.
Raut was arrested for his expression of peaceful political opinions, the US-based rights body said.
Nepal should amend its practices to comply with international and domestic standards to protect freedom of expression, it said.
Raut was arrested Sep 14 for allegedly advocating that the southern plains of Nepal, known as the Terai, be allowed to secede from the rest of the country as part of a long-standing debate on state restructuring.
On Oct 8, he was charged with sedition, presumably under the Crime against State and Punishment Act 1989 which forbids any "attempts to cause any disorder with an intention to jeopardise sovereignty, integrity or national unity of Nepal".
The crime carries a penalty of life imprisonment.
Police also said that Raut had written articles and books advocating secession by Madhesis, the Terai community.
There is no evidence that Raut advocated the use of violence, or that his actions led to violence, Human Rights Watch said.
