Should states/regions etc. have a right to secede from their nation-states?

[Grand Wizard Lizard of the Klan]

If state is unitary only after long proces preparing such part of country to secede.
If federation I see no problem as it would be simpler from the technical point of view.
Of course as long as that state is republic. If monarchy I guess only good solution of that problem is to secede that part of country which want to be separate country as some sort of liege country or separate kingdom having it own monarch from reigning family. Although I am not sure if such situation will be legitimate and not against basic laws. This is interesting issue, I should think more about : I