You are right. There was this thing that invokes the power of "Nature, and of Nature's God", which I take to mean the almighty. A bunch of subsequent rules agreed to by a bunch of men has no power in comparison to that.
There was a long list of legitimate grievances which the colonists had for years attempted to negotiate, without success.
If you will read the document, it points out that mentioning the grievances is only a courtesy, not a requirement.
a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation
In the case of Southern Secession, there was no need to list causes, because the "causes" had been the subject of debate throughout the Nation for decades.
and before any Union army invaded a single Confederate state.
And once again, if you will read the thread, specifically the items posted by PeaRidge regarding the messages from Lincoln and other Union officials, you will discover that an invasion fleet was ten miles away from Ft. Sumter and ready to land. The Union was invading, they just stopped the mission after they heard that Ft. Sumter was under attack.
Most likely it was the knowledge of the arrival of the Union fleet that precipitated the attack.
But several seceding states did officially list their reasons for secession, links have been posted here already, here for example is Mississippi's.
DiogenesLamp: "...an invasion fleet was ten miles away from Ft. Sumter and ready to land.
The Union was invading, they just stopped the mission after they heard that Ft. Sumter was under attack."
But there was no "invasion", it was a pre-announced resupply mission to Union troops in Union Fort Sumter.
It was no more an "invasion" than US ships sent to resupply or reinforce Guantanamo Bay, Cuba.
The decision to use this mission as an excuse to launch military assault on Fort Sumter was strictly Jefferson Davis', who gets full blame or credit for all the resulting war's death & destruction.