Quite the contrary, North Carolina had made it's position clear before the blockade was extended. Let's look at the proclamation first, dated April 27, 1861. The body of it states as follows:
Whereas, for the reasons assigned in my proclamation of the 19th instant, a blockade of the ports of the States of South Carolina, Georgia, Florida, Alabama, Louisiana, Mississippi, and Texas, was ordered to be established; and, whereas, since that date public property of the United States has been seized, the collection of the revenue obstructed, and duly commissioned officers of the United States, while engaged in executing the orders of their superiors, have been arrested and held in custody as prisoners, or have been impeded in the discharge of their official duties without due legal process by persons claiming to act under authority of the States of Virginia and North Carolina, an efficient blockade of the ports of those States will therefore also be established.
Virginia is not an issue. They had issued a ordinance of secession ten days earlier. They were in a state of rebellion as of that time and Lincoln was quite correct in extending the bolcade to them. They should have been included in the original proclamation.
What about North Carolina? While it is true that the North Carolina declaration of secession was dated May 20, that was a mere formality and their actions had been hostile to the United States for some time. On April 15, state authorities siezed Fort Macon. A day later they siezed Fort Carswell and Fort Johnston. On April 21st the state siezed the branch mint at Charlotte and on the 22nd they siezed the U.S. Armory at Fayetteville. There was no doubt that North Carolina had joined the rebellion and Lincoln didn't need a formal declaration to recognize that. The blockade was justified.
[You]: What about North Carolina? While it is true that the North Carolina declaration of secession was dated May 20, that was a mere formality and their actions had been hostile to the United States for some time. On April 15, state authorities siezed Fort Macon. A day later they siezed Fort Carswell and Fort Johnston. On April 21st the state siezed the branch mint at Charlotte and on the 22nd they siezed the U.S. Armory at Fayetteville. There was no doubt that North Carolina had joined the rebellion and Lincoln didn't need a formal declaration to recognize that. The blockade was justified.
Well, was it? Let's read John Nicolay, no friend of the South:
As a necessary part of the conspiracy [Nicolay is always calling it a "conspiracy"], the governors of the Cotton States now, by official order to their extemporized militia companies, took forcible possession of these forts, arsenals, navy-yards, custom-houses, and other property, in many cases even before their secession ordinances were passed. This was nothing less than levying actual war against the United States, though as yet attended by no violence or bloodshed. The ordinary process was, the sudden appearance of a superior armed force, a demand for surrender in the name of the State, and the compliance under protest by the officer in charge -- salutes to the flag; peaceable evacuation, and unmolested transit home being graciously permitted as a military courtesy.
There is a remedy short of war for these expropriations of federal property: Article III, Section 2, shows that Lincoln had recourse to the Supreme Court, to compel the North Carolina to return his facilities. Rather than displaying overt hostility (gunfire? verbal unpleasantries? finger-gestures at 20 paces?), North Carolina was still in the Union, and Lincoln's complaints, as of his levying the blockade against them, were only 12 days old, as from the earliest date in your chronology. Lincoln chose war as his first option. You, following Lincoln, seem to regard anything short of that as "a mere formality".
As for Nicolay's claim that these acts added up to "nothing less than levying actual war against the United States", I think he says that just because he has his eye firmly fixed on the definition of treason in Article III, Section 3, which is one of his principle objectives in writing his book: by blackening Southerners, to exonerate Lincoln of the political charge that he desired to levy war on the South, and that his actions were undertaken not as responses to "treason", but as initiatives he undertook himself, to lay the South under martial law and the Republic at his feet.