The Framers gave Congress the power to regulate commerce, not to compel it, and for over 200 years both our decisions and Congress's actions have reflected this understanding. There is no reason to depart from that understanding now. [p. 24]I agree with the first sentence. Congress does not have the constitutional power to compel commerce, either interstate or intrastate. This should be thought to be the case regardless of Congressional actions in support or to the contrary.
I find the conceptual view implied by the second sentence to be of concern. The second sentence seems to me to imply that if Justice Roberts did believe there was a reason to depart from "that understanding," then he might have been willing to make that departure by way of the Court's opinion at hand. If this is not implied, then it seems to me Justice Roberts would have chosen to leave this sentence out of his opinion. I wish he had.
So, why is this of concern? I think the conceptual view implied by this sentence is that, when useful, the Court should change the way the Constitution is understood by way of Court opinions. Of course, the proper, constitutional way to change the meaning of the Constitution is to amend the Constitution. Article V specifies the proper way to change the meaning of the Constitution, and the proper way does not include a grant of power to the Court to do so.
The Court should make the constitutional view clear, nor murky as I think this sentence does. If it seems appropriate to point out there is no reason to depart from the historical understanding of the Constitution now, then I suggest that Justice Roberts should also add: "and if there was reason to change this understanding, then the Court cannot and will not attempt to do that. If there is such reason, then the constitutional way of changing the meaning of the Constitution is to carry out the requirements found in Article V."
Sadly, for me, it seems that long ago most of the Justices have come to see their constitutional role in the conceptual way implied by this quote.