The main way it was a Federal vs States Rights issue was that the Confederacy was unhappy that the free states had rights and did their best to undermine them by means of such things as the Fugitive Slave Act of 1850 and the decision in Dred Scott v. Sandford. If you read the The Declaration of Causes of Seceding States (that is why the seceding states claimed at the time they were seceding) you find such little gems as Georgia’s.