No State, upon its own mere motion, can lawfully get out of the Union;
Perpetuity is stamped upon the Constitution by the blood of our fathers. For this purpose was the principle of amendment inserted in the Constitution which all have sworn to support and in violation of which no state or states have the right to secede, much less dissolve the Union.
Jackson was reacting to the claimed right of South Carolina to nullify Federal tariffs and other Federal laws.
The right of a State to secede is not an open or debatable question
A large body of people, sufficient to make a nation, have come to the conclusion that they will have a government of a certain form. Who denies them the right? Standing with the principles of '76 behind us, who can deny them the right? ... I maintain on the principles of '76 that Abraham Lincoln has no right to a soldier in Fort Sumter. ... You can never make such a war popular. ... The North never will endorse such a war.
A team of British lawyers has now concluded that the Declaration of Independence was illegal, and the American colonies had no right to secede from England. Well, you thought our court system was backed up.
The Union was formed by the voluntary agreement of the States; and these, in uniting together, have not forfeited their Nationality, nor have they been reduced to the condition of one and the same people. If one of the States chose to withdraw its name from the contract, it would be difficult to disprove its right of doing so.