The 10th amendment had nothing to do with the right of secession.
10th Amendment
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
I think the power to leave could be covered under this provision. More convoluted interpretations of the constitution have certainly been made by our illustrious courts. I have a hard time believing our freedom loving forefathers would have agreed to enter into a union that they couldn't leave especially after they had just fought for their freedom.