John Marshall, whose opinion in Marbury v. Madison (1803) famously declared that "It is emphatically the province and duty of the judicial department to say what the law is," also wrote the opinion in Ex Parte Bollman and Swartwout (1807) declaring that suspension of habeas corpus was a power vested only in the Congress. Lincoln simply ignored the law.
I read up on Ex Parte Bollman and, although some don't believe that Wikipedia should be taken seriously, if you believe what it says here, I take this to have a different interpretation:
Only Congress may suspend the writ of habeas corpus.
To me, a matter-of-fact observation means just that. That it can't be construed as official precedent. And if it was just the Chief Justice expressing an opinion, without input from the other justices, it holds even less water.
- This was not so much an argued point, nor something presented as a new interpretation, as it was a matter-of-fact observation made by Chief Justice John Marshall. This principle would be much more hotly debated in the later Supreme Court Cases of the American Civil War, which centered around wartime civil liberties and the ability of the various branches of government to control them.