[central_va]

Was it constitutional when Lincoln:

1. Arrested the MD legislature
2. Suspended Habeas Corpus
3. Issued The Emancipation Executive Order
4. Ordered the arrest, military trial, conviction, and sentencing of Vallandigham

Need I go on?

[jmacusa]

Yeah General. Check out article 1 sec.9 of the Constitution.

[BroJoeK]

central_va: "Was it constitutional when Lincoln: 1.Arrested the MD legislature...

You can answer all such questions yourself if you'll only remember the date May 6, 1861.
That is the date the Confederacy formally declared war on the United States.
On May 6, 1861 Union state citizens supporting the Confederacy met the Constitution's definition of treason:

"Article 3, Section 3:
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort."

Treason is punishable by Federal law, and after May 6, 1861, those Union state citizens supporting the Confederacy met conditions of that law.