I answered that question. They wanted to secede because the federal government wasn't enforcing federal law, specifically the escaped slaves act. States were using their own courts and their own legislatures to free slaves, and the federal government was not willing to override states' rights. The states' right to own slaves was not in jeopardy at that time. The only states' right that the secessionists wanted to avail themselves of was the right to secede, which they didn't actually have.