Secession?

Constitution of the Confederate States of America states in section 9:

"Section 9 - Limits on Congress, Bill of Rights

1. The importation of negroes of the African race from any foreign country other than the slaveholding States or Territories of the United States of America, is hereby forbidden; and Congress is required to pass such laws as shall effectually prevent the same." (http://www.usconstitution.net/csa.html#A1Sec9)

The Union did not tell the general public this fact.
When explaining to the general public about the issue of slavery, went for the 'emotional vein' in order to influence abolitionists. They used emotions rather than straight facts to ensure that the common american would vote in their favor.
As if the average american is too stupid to understand straight facts and formulate their own opinion.

Also in the document that the South wrote about their secession was completely 'right'.

"On the 4th day of March next, this party will take possession of the Government. It has announced that the South shall be excluded from the common territory, that the judicial tribunals shall be made sectional, and that a war must be waged against slavery until it shall cease throughout the United States.

The guaranties of the Constitution will then no longer exist; the equal rights of the States will be lost. The slaveholding States will no longer have the power of self-government, or self-protection, and the Federal Government will have become their enemy.

Sectional interest and animosity will deepen the irritation, and all hope of remedy is rendered vain, by the fact that public opinion at the North has invested a great political error with the sanction of more erroneous religious belief." (http://www.sonofthesouth.net/leefoundation/secession_causes.htm)

They believed that the government was being unconstitutional, therefore any agreement that they had with the union based upon the constitution (which they believed the government had violated) was completely null.
Which... they were completely right. Even if I don't think they should have done what they did to the slaves.

Yup random ramblings about what I found in history today :D