The law was set shortly after the Civil War in Ex parte Milligan 71 U.S. 2 (1866): "Neither the legislature nor any executive or judicial officer may disregard the provisions of the Constitution in case of emergency"

Why wasn't this invoked prior or during COVID?  

This was the ruling of the United States Supreme Court shortly after the Civil War in Ex parte Milligan, 71 U.S. 2 (1866) which yet stands to this day and neither the legislature nor any executive or judicial officer may disregard the provisions of the constitution in case of emergency 

How to tell if you are a below-average lawyer who barely passed the bar without telling me you're a below-average lawyer who barely passed the bar.   https://t.co/8yBl0h55X1

— Tom Luongo (Head Sneetch) (@TFL1728) September 10, 2023