It was simply never established in court that the Souths secession from the Union was illegal.
Same situation that made the colonies leave Englands rule earlier which started the Revolutionary War.
http://www.civilwarhome.com/secessionjustification.htm
http://www.secessionist.us/legality_of_secession.htm
The Undeniable Legality of Secession
At the most fundamental and basic level of our political belief system as Americans rests the idea that men ought to be free to determine their own form of government. Our Declaration of Independence states this fact clearly:
...That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness...
Few Americans would deny that our founders in 1776 had among other inalienable rights the justification and right to assert a form of government "most likely to effect Safety and Happiness". With such a strong sense of the rights of the people inherent in our most foundational of beliefs, it is amazing that Americans so easily view these concepts as applicable only to another time and place.
Secession is legal under natural law, biblical law and in accordance with the State-Federal compact theory of government.
The Undeniable Legality of Secession
At the most fundamental and basic level of our political belief system as Americans rests the idea that men ought to be free to determine their own form of government. Our Declaration of Independence states this fact clearly:
...That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, --That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness...
Few Americans would deny that our founders in 1776 had among other inalienable rights the justification and right to assert a form of government "most likely to effect Safety and Happiness". With such a strong sense of the rights of the people inherent in our most foundational of beliefs, it is amazing that Americans so easily view these concepts as applicable only to another time and place.
Secession is legal under natural law, biblical law and in accordance with the State-Federal compact theory of government.
The Unconstitutionality of Using Force to Coerce a State
President James Buchanan stated succinctly in a speech before Congress, December 1860 that the Constitution does not delegate to the Federal government the power to use force against a state:
"The question fairly stated is, Has the Constitution delegated to Congress the power to coerce a State into submission which is attempting to withdraw or has actually withdrawn from the Confederacy? If answered in the affirmative, it must be on the principle that the power has been conferred upon Congress to declare and to make war against a State. After much serious reflection I have arrived at the conclusion that no such power has been delegated to Congress or to any other department of the Federal Government. It is manifest upon an inspection of the Constitution that this is not among the specific and enumerated powers granted to Congress, and it is equally apparent that its exercise is not " necessary and proper for carrying into execution " any one of these powers. So far from this power having been delegated to Congress, it was expressly refused by the Convention which framed the Constitution."
http://www.etymonline.com/cw/secession2.htm