IEEPA was what Trump felt was most
Immediately at hand and least constrained. It’s now been confirmed that he acted illegally. Any further actions he takes will be more constrained, and less able to be perpetuated indefinitely and unilaterally.
He has been talking for months about how much trouble the country is in if SCOTUS decides the way it decided today. So, he at least doesn’t seem to find it minor.
What SCOTUS did not resolve today is the repayment of hundreds of billions of dollars in tariffs that were illegally collected. A lot of businesses will have lawsuits ready to file Monday (if not today) on that issue. The U.S. government potentially faces hundreds of billions of liabilities in treating taxes that they never should have collected from Americans. That will be a mess.