[BroJoeK]

DiogenesLamp referring to the original Constitution's Fugitive Slave clause and Compromise of 1850 Law: "The Constitution is not amended by "compromise".
It is amended by a clearly enumerated process.
Nothing short of a constitutional amendment will repeal that clause in Article IV."

But no challenge was ever made in the Supreme Court on constitutional grounds, to the Compromise of 1850 Law, which moved responsibility for returning Fugitive Slaves from Northern States to the Federal Government.
Slave states which objected to the Compromise of 1850 could easily have challenged it in Court, and with Judge Roger Tanney its Chief Justice, likely have succeeded.

But of course, they did not, since it was a Compromise they heartily supported.

[DiogenesLamp]

But no challenge was ever made in the Supreme Court on constitutional grounds, to the Compromise of 1850 Law, which moved responsibility for returning Fugitive Slaves from Northern States to the Federal Government.

That "no challenge was ever made" means what in terms of constitutional validity? Are we to accept this as a new standard for constitutional law? Congress can make changes, and they are valid if nobody challenges them?

And here I thought we had this amendment process.