Yea, it's called the EXPANSION of slavery into free states and free territories yet to become states.
So what you’re saying is that those other States and Territories didn’t have the right to decide for themselves which path to follow? Am I understanding you correctly?
What, then, did the 10th Amendment to the US Constitution mean then? Rights are rights, whether they’re popular or not. Those States and Territories had the right under the US Constitution to decide for themselves which path they would choose, even if one path was morally bankrupt.
After all, if what you say is true, and the States do not have a right to determine their own future, then which is worse; the States determining that chattal slavery was acceptable or the Federal Government determining that Infanticide was acceptable? Both have, at their heart, the debate of what is considered human life and what role the Federal and State Governments have in protecting or destroying that life.