Secession is the god given rights for all non-state nations and as well all ethnic groups, so long as the one wanting to secede could stand on its own.

In principle if a group of people who likes to consider itself as an ethnic group or nation could secede from an existing nation-state, if the people concerned are for it. It is a birthright given thing and no one could take it away.

As such, an ethnic group or non-state nation could sign that it won't secede from a union a hundred times but could decide to leave the voluntary or involuntary union when and if the people decided to leave the country they are incorporated into. It is the democratic group rights a group of people and the value and desire of the people could change according to the space and time of the prevailing political conditions.