He exercised the authority granted him by Article II section 2 of the Constitution. “The President shall be the Commander in Chief of the army and navy of the United States and of the militia of the several states, when called into service of the United States. A Naval blockade of a hostile or belligerent’s ports is recognized in International law as a legitimate exercise of Naval power during war. Lincoln’s legitimate use of this tactic was confirmed by the Supreme Court of the United States in the case 67 U.S. 635 aka Amy Warwick v. the United States. In this case several New England ship owners sued the Federal government over their ships be seized by blockading forces and the cargos condemned and ships sold. The owners argument was that since no war was declared by Congress, the President lacked the authority to impose blockade. The Court found that even though no official declaration of war existed, the Confederacy, through two specific acts of war against the United States (the firing on Fort Sumter and the issuance of the Privateer Act which authorized letters of Marquis to Southern ship owner to seize U.S. ships) that a state of war existed between the United States and the Confederate States. Since a state of war existed de facto, Lincoln, as C-in-C could call for the blockade without an official declaration of way by the Congress.
The international community recognized the legitimacy of the Union blockade of Confederate ports. Every maritime country in Europe including England, the greatest maritime and Naval power of the century warned their merchant fleet
that they sailed at their own peril if they carried contraband cargos to the blockaded Confederate port. Over the course of the war, the U.S. Navy captured, sank or otherwise destroyed 1504 ships. A large percentage of those ships were of British owned, registered and crewed.
Only once did the British Government protest the capture of a British ship, and that was the RMS Trent. However, in a judicial opinion drafted by the Queen’s Advocate, The Crown Prosecutor and the Crown Solicitor for the Prime Minister Lord Palmerston, they found that Captain Wilkes had acted incorrectly. Had Wilkes put a prize crew aboard the Trent, sailed her to a U.S. port and submitted the seizure to an Admiralty court for adjudication the British would not have objected to the fates of Mason and Slidell. Wilkes would have been acted within the law as the British saw it. Wilkes however, did not do this. He searched the Trent, removed Mason and Slidell and their documents and allowed the Trent to proceed on its way. This is what violated the law as the British saw it. Be that as it may, Lincoln smoothed the ruffled English feathers and for the rest of the war, the greatest maritime and naval power on the globe allowed Abe Lincoln’s blockade to continue un hindered by British sea power. Both the Supreme Court of the United States and the British Empire found Lincoln’s blockade to be legal within the law as it existed at that time. On a side note, Davis’s issue of letters of Marquis to Confederate privateers was illegal under the Paris Declaration of 1856. This international pack outlawed privateers. The United States was not among the 45 signatory nations to this pact. Lincoln advised the British, French and Spanish Governments that the United States would strictly adhere to the provisions of that treaty, even though the U.S. was not a signatory.
Left to their own devices, Lords Palmerston and Russell would likely have recognized the Confederacy and worked to its benefit in various important ways such as allowing the Laird shipyard to complete CSS Mississippi and CSS North Carolina. It was in great Britain's interest to see the Union divided into two countries.
Queen Victoria's beloved husband Prince Albert of Coburg was on his deathbed and called for Palmerston and Russell with Victoria present, and begged them not to help the Confederacy and to thereby affiliate Great Britain again with slavery. Palmerston and Russell agreed to his dying wish.
The establishment of a blockade is itself an act of war but Lincoln usually wanted to operate under the fiction that the eleven Confederate states were still part of the Union. Unless, of course, he wanted to blockade Confederate ports which required recognition of the Confederacy as a belligerent but quite separate nation or when, without the concurrence of the Virginia legislature he proceeded to have Congress carve West Virginia out of Virginia's territory or when, after his death, the Radical Republicans REQUIRED of the defeated states of the Southland as a CONDITION OF "RE-ADMISSION" to the Union, those states were required to "ratify" proposed Amendments 13, 14 and 15 to the Constitution. How can a state be "re-admitted" when, according to Dishonest Abe the state could not have left? How does a nation make war against what it claims are its own people? That is not what is meant by war for purposes of justifying blockades.
How thoroughly Lincolnian to promise to obey the Paris Declaration of 1856 without, well, actually signing it!
The SCOTUS case you cite might be more persuasive if, instead of noting that Congress DID NOT declare war, it had taken into account that since the Union did not recognize the Confederacy as a nation, Congress COULD NOT declare war against it. This is a rare case in which the Chase SCOTUS joined the rest of the Union's leadership in becoming irrational whirling dervishes, wrapping themselves into pretzels to avoid the obvious: that the Confederay was a full-fledged nation whether Lincoln and his radical pals wanted to admit it or not.
600,000 combatants died because Lincoln was going to wage war to impose his ideology under cover of "suppressing insurrection" in a nation born in insurrection. Lincoln himself in his first Inaugural Address cited in full elsewhere in this thread conceded our revolutionary heritage that when government has become intolerable to its subjects they are entitles to rebel against that government and overthrow it.
The Southland sought to rebel on behalf of 11 states and to let the rest decide whether the rest were satisfied. South Carolina wanted to reclaim its freedom and let New Jersey decide whether it was satisfied with the existing government. It is fair to say that New York City NEVER supported Lincoln's war. They should have held a referendum.
One of the most important freedoms is the freedom to leave, whether as a state or as an individual. We ought to have aspired and we ought to aspire to be a society which does not seek to imprison its states or its citizens simply because either wishes to leave.