At issue is a law from 1867 known as the Anti-Injunction Act. The basic thrust of that law is it prohibits lawsuits against a tax until that tax has been levied and collected.
Fast forward to 2012, and the tax penalty linked to the invidiual mandate has not been applied as yet - so the legal theory is very clear - no one has standing at this point to challenge the individual mandate penalty in court.
"That succeeded in one lower court," said legal scholar Thomas Miller of the American Enterprise Institute, but like many other legal experts, Miller does not see this derailing the Obama health law challenges.
"I think the Court will finally decide they can go forward; this is a big case," Miller said.
In many forums on the legal challenge to the Obama health law, this question presented on the first day of arguments is almost always glossed over - I watched hours of different legal preview events in recent weeks and there was bare mention of it as a real possibility.
But it is important to note that sometimes, the Justices will look to find a way to side step a major issue, and wait for it to return at a later date.
"It is an obscure provision in the IRS code," acknowledged Kent Streseman of the Chicago-Kent College of Law.
"The bottom line is it could stop the Affordable Care Act litigation in its tracks," said Streseman, "and prevent courts from hearing these suits until basically April of 2015."
What's really interesting about this first day is that no one brought this issue before the Court on appeal - instead, the Justices decided that they wanted to hear arguments on this matter.
So, while I'm not even close to being a legal expert, that tells me there was some support among the Justices for seriously looking at this option.
Because there was no "plaintiff" so to speak, on this matter, the Court actually appointed a lawyer to make the case, as attorney Robert A. Long, Jr., gets the honors on Monday.
Is it a tax or not?
The Washington Examiner weighs in.
Transcript of day 1 on ACA SCOTUS hearing.
Verilli's "uh-oh" moment . . .
“General Verrilli, today you are arguing that the penalty is not a tax. Tomorrow you are going to be back and you will be arguing that the penalty is a tax,” said Justice Samuel Alito, in one of the few laugh lines throughout the 90 minutes of argument Monday.