If I remember correctly if it was a tax then it was considered unconstitutional was the main argument being made. Some conservative judges decided to admit it was a tax, but then agreed with the Democrat appointed justices to allow it anyways.
Article III, Section 2, Clause 1 we set the limits of our SCOTUS and of any inferior federal courts that
our servant Congress creates…“The judicial Power shall extend to all Cases, in Law and in Equity, arising
under this Constitution, the Laws of the United States, and Treaties made...; to all cases affecting
Ambassadors, other public Ministers and Consuls; to all cases of admiralty and maritime Jurisdiction; to
controversies to which the United States shall be a Party; to Controversies between two or more States;
between a State and Citizens of another State; between Citizens of different States; between Citizens of
the same State claiming Lands under Grants of different States; and between a State, or the Citizens
thereof, and foreign States, Citizens or Subjects.”
So.
We stipulate that SCOTUS and inferior federal courts only have jurisdiction if a case arises under the
Constitution, under federal laws or treaties, or if these United States are parties to the case, etc.; in
other words, if a case arises under laws or treaties that violate the U.S. Constitution we do not let our
servants decide, “Oh, trust us; this is a federal matter”. No; we sovereigns decide that.
the Supremacy Clause (Article VI, Section 2) we stipulate: “This Constitution, and the Laws of the
United States which shall be made in Pursuance thereof…shall be the supreme Law of the Land…”. That
means any federal law creating an office or activity not ‘in pursuance of’ the U.S. Constitution – in other
words, not enumerated in it – is of no force or effect.