That part of the Constitution was also written at a time when we were still debating on if we were going to have a standing military. The original wording allowed for those state militia to be called up to national service if the fed needed them. Slave-owning members of the Constitutional Convention who represented the South rejected this idea that the federal government could call up their militias because it would leave their states with no one to protect them from slave uprisings. These militias collaborated with the Southern Slave Patrols.