I should have said, "I am aware that is your claim".
"In the meantime, I'll reiterate that the Shreveport decision doesn't support your position."
It does in the sense that the USSC ruled that Congress may regulate intrastate commerce if it substantially affects their interstate regulatory efforts. In this case, it was to negate the advantage that one carrier had over the others, thereby impeding competition.
The bottom line? It brought intrastate commerce into Congressional regulatory play. That you cannot deny, and that's what makes the case significant.
No, it ruled that Congress may regulate intrastate commerce if it substantially hinders interstate commerce.