What section of the Constitution did he violate by sending the ships to resupply Sumter?
"What section of the Constitution did he violate by sending the ships to resupply Sumter?"
Well, first of all, you are mixing two issues. Constitutionality and re-supply.
At the time,everyone, I repeat, everyone knew that sending Federal troops to Charleston was an act of war.
If there were a real concern that the troops be re-supplied, all Lincoln had to do was authorize the Union quartermaster at Ft. Sumter to order and accept supplies from the Charleston authorities. He had money on deposit for such requests, and this is the way the men had been fed since construction had begun 25 years before.
If Lincoln did not trust that transaction, then he could have shipped the supplies down by railroad.
Putting supplies on armed Federal warships with several hundred armed men was carrying it too far.
What constitutional authority did he have for this provocative and aggressive action?