Marbury v. Madison 1803, vol 5, pg 137
It is also not entirely unworthy of observation that, in declaring what shall be the supreme law of the land, the Constitution itself is first mentioned, and not the laws of the United States generally, but those only which shall be made in pursuance of the Constitution, have that rank.
Thus, the particular phraseology of the Constitution of the United States confirms and strengthens the principle, supposed to be essential to all written Constitutions, that
a law repugnant to the Constitution is void,
and that courts, as well as other departments, are bound by that instrument.
Norton v. Shelby County, 118 U.S. 425 (1886)
While acts of a de facto incumbent of an office lawfully created by law and existing are often held to be binding from reasons of public policy, the acts of a person assuming to fill and perform the duties of an office which does not exist de jure can have no validity whatever in law.
An unconstitutional act is not a law; it confers no rights; it imposes no duties; it affords no protection; it creates no office; it is in legal contemplation as inoperative as though it had never been passed.
A law repugnant to the Constitution is NOT void until a court finds it in conflict with the Constitution.
For easily confused folks the land referred to in the Supreme Law of the Land, aka the Constitution, is the United States of America, aka, America.
Public opinion does not trump court decisions.