Secession in the United States Wikipedia

This is a useful summary.

The delegates to the Philadelphia Convention convened and deliberated from May to September 1787. Instead of pursuing their official charge they returned a draft (new) Constitution, proposed for constructing and administering a new federal—later also known as "national"—government. They further proposed that the draft Constitution not be submitted to the Congress (where it would require unanimous approval of the states); instead that it be presented directly to the states for ratification in special ratification conventions, and that approval by a minimum of nine state conventions would suffice to adopt the new Constitution and initiate the new federal government; and that only those states ratifying the Constitution would be included in the new government. (For a time, eleven of the original states operated under the Constitution without two non-ratifying states, Rhode Island and North Carolina.) In effect, the delegates proposed to abandon and replace the Articles of Confederation rather than amend them.

Because the Articles had specified a "perpetual union", various arguments have been offered to explain the apparent contradiction (and presumed illegality) of abandoning one form of government and creating another that did not include the members of the original.^[b] One explanation was that the Articles of Confederation simply failed to protect the vital interests of the individual states. Necessity then, rather than legality, was the practical factor in abandoning the Articles.

This discussion of the betrayal and unconstitutionality of the Philadelphia Cconvention still leaves largely untouched a discussion of deeper problems, noted by Bailyn, and Palmer, regarding confederated government established by "the people" in the first place, and resulting issues raised regarding modification, secession, and problems of validity, constitutionality,  and change, in general. Palmer's discussion may be the best on this issue, but I haven't read much of Maier's treatment. 

The important point here, and one made, as I recall, by Palmer, but perhaps Bailyn had seen the issue as well, is that the structural and practical problems created by this kind of constitutional rubric were and still are insoluble.