The Supreme Court case Dred Scott vs. Sandford was one that essentially stated that slaves are property and have no legal rights that white citizens were bound to respect. With this ruling, the Supreme Court established the example that slavery can exist anywhere within the US, even in states that allowed slavery.
This shows the idea of nullification, because it allows a state to void (aka nullify) a law that they deem as unconstitutional. Northern states would use this concept in order to stop slavery from happening their states.
This also restricts the ability of the federal government to restrict the expansion of slavery, as this court case gives Southerners the legal right to bring their slaves wherever they want without facing penalty from the federal government.