Why did southerners who supported secession believe the action was constitutional?

Southerners who supported secession believed it was constitutional based on the principle of states' rights, arguing that the U.S. Constitution was a compact among sovereign states that allowed them to withdraw if they felt their rights were being violated. They contended that the Tenth Amendment granted states powers not explicitly given to the federal government. Additionally, many believed that their right to secede was rooted in historical precedents and the founding principles of self-determination. This perspective was particularly fueled by tensions over issues like slavery and federal authority.