Not their job, man.
It may not be the USSC’s job, but when the executive branch and states refuse to exercise their constitutional right to ignore or not enforce unconstitutional laws (as Jefferson and Madison clearly stated in their Kentucky and Virginia resolutions), then by default the USSC has the last word on what is or is not constitutional. Regarding the commerce clause clause, they’ve eliminated it.
Until we get a governor or president like Andrew Jackson who tells the USSC to shove it, then we will be continued to be governed by the USSC which finds everything constitutional.