https://www.tourolaw.edu/2ndcircuit/november96/96-2060.html
Now, what was the basis for your assertion that " they have exceeded their Constitutional Authority, and these laws are for that reason illegitimate?"
Now to substance. Yes, the courts have ruled consistently (in recent years) in favor of the modern expansive interpretation of our Constitution. They have in effect nullified almost any restrictions on Federal power via a grossly expanded interpretation of the so-called "commerce" clause in Article I, Section 8. A proper reading of that clause, interpreted in light of the Founders' own writings, is that the intent was to prevent the several State Governments from erecting, between the States, any of the various barriers to trade that were common at the time. The intent was emphatically not to empower the Federal Government to regulate any private activity which might, by some feverish stretch of imagination, affect interstate commerce in some way.
You may choose to dismiss this as "groundless", or just "my" opinion, but there is overwhelming Constitutional scholarship to support my assertion. After all, what is the point in writing a document to explicitly define and restrict the powers of a central government, while including language which frees that government of nearly all restrictions?
That the courts presently rule otherwise is, in my opinion and among other things, a symptom of (and fallout from) the infamous attempt by FDR to "pack the court" when the Supremes balked, on Constitutional grounds, at accepting his socialist "New Deal".