In what ways did Lincoln violate the constitution when in office?

It is contended by some historians that Abraham Lincoln violated the Constitution of the United States in a number of ways while he was in office. Among these violations are the following: 

• The right of secession

The founding fathers, especially Thomas Jefferson, recognized the states' right to secede. While he did not advocate the exercise of this right, Jefferson did recognize that the right to secede remained with the states.

This was a right that continued throughout the initial drafts of the Articles of Confederation, the Constitution and the Declaration of Independence.

But, Lincoln did not recognize the Constitutional right of the Southern states to secede.

• The right to declare war

The right to declare war rests with the Congress; however, President Lincoln ordered the military blockade of the ports that belonged to the South. This was an act of war, but Congress had not approved of it. (Interestingly, 75% of the tariffs paid to the Federal government by ports in the U.S. were paid by the Southern ports.)

Some historians contend that President Lincoln also committed treason since he declared war on his own country since he did not recognize the South's secession and did not recognize the Confederacy as a sovereign state. 

• Suspension of writ of habeus corpus
  

A state legislator from Maryland, John Merryman, was arrested for his attempts to prevent Union troops from passing from Baltimore to Washington at the time of the Civil War. After this, Merryman's attorney sought a writ of Habeus Corpus, hoping that a federal judge would examine the charges. But, President Lincoln suspended the right of Habeas Corpus, and the commanding officer of Fort McHenry would not turn Merryman over to authorities. This is another violation of the Constitution.

• Suspension of civil liberties

Lincoln ordered several Northern newspapers shut down that wrote against him, and he had several city officials of Baltimore arrested.

He ordered the arrest of Chief Justice Roger Taney after he ruled that Lincoln had violated the Constitution after he had illegally suspended the Writ of Habeus Corpus.