The right to secede is often claimed by separatists and rejected by federalists - the matter is problematic because few national constitutions are written with an exit clause. A strong separatist movement has prompted two sovereignty referendums in Quebec, and western alienation has led to informal talk about separation in Alberta. In 2000, the government of Canada passed the Clarity Act, which made it the perogative of the house of Commons whether a province could secede from Canada or not.
[+] six questions on the right to secede.
On Some Advantages of Constitutionalizing the Right to Secede -