Discuss the term “States’ Rights” in the context of the antebellum South.

Intellectually, the idea of states' rights was based on
the idea that the Constitution and the Union was an agreement between sovereign states,
not between all the individuals of the country.  People who believed this also believed
that states had the right to dictate the terms of their involvement in the Union. 
Because of this, they had the right, for example, to nullify federal laws as South
Carolina tried to do in the early 1830s and they had the right to secede, just as the US
would have the right to pull out of the UN
today.

Practically speaking, the idea of states' rights was
all about slavery.  The South's demand for states' rights was really based only in their
desire to preserve the system of slavery.