He claims the South actually opposed states’ rights, that is, the rights of the Northern states to oppose slavery. It is an opinion being stated. He then goes on to quote from South Carolina’s “Declaration of the Immediate Causes Which Induce and Justify the Secession of South Carolina from the Federal Union” from 1860 which complains of the Northern states failing to “fulfill their constitutional obligations” in returning runaway slaves (a process already upheld by the Supreme Court) or allowing slaveowners to travel through the state with their slaves.
Through the example he has given, I can see that he is absolutely correct in stating they opposed those States’ Actions (not any supposed Rights), or more succinctly put: the rights of those several States to ignore the Constitution and the Federal Courts. And one can easily see how some people would object if a law was upheld but the States were not reprimanded for failing to uphold the law. It is this lawlessness to which they were objecting. Even if we, today, can see there was something fundamentally wrong with that law – even though the Supreme Court had upheld it – but we also know that we cannot allow people to randomly decide which laws they will live by. That spells trouble in any society, then or now.
The Abolition Movement had been growing for some time and it seems a lot of people in some states simply ignored the Federal Courts and did what they thought morally correct. It might have been morally correct, but not legally correct. And the Federal Government had gotten lax about enforcing certain provisions of the law. That was the objection of the South Carolina convention, not the flippant response Loewen seems to think suffices.