That's incorrect. It's actually "only now" that the 10th amendment is being interpreted as an affirmative limitation on federal power. Historically, the 10th amendment was considered a mere truism. U.S. v. Darby (1941).
Conceptually, how the Constitution works is as follows. The states inherited the sovereignty and unlimited power of the British parliament. In aggreeing to the Constitution, the states delegated some of that power to the federal government, and agreed to refrain from the exercise of certain other powers. The clauses of the Constitution outline the powers delegated and prohibited. All the 10th amendment says is that anything that hasn't been delegated or prohibited hasn't been delegated or prohibited. Which is tautological.
The mere face of the text cannot support an interpretation that the 10th amendment does anything other than state the obvious. If a federal action is otherwise Constitutional, by virtue of falling into one of the delegations, then it is by definition something that has not been reserved to the state.
The Progressive movement's attempts to circumvent federalism date to the beginning of the 20th century, so you can hardly cite a 1941 case to defend your assertion. That was four years after FDR's court packing scheme and eight years after the formation of the National Recovery Administration.
As far as I can tell, you only see the Tenth Amendment as a tautology because you take for granted the makeup and principles of the American government. It was not at all a given at the time that the Federal government would leave sovereignity to the states and only exercise certain defined powers. For example, it has largely ceased to do so today, in violation of the Tenth Amendment.
All the 10th amendment says is that anything that hasn't been delegated or prohibited hasn't been delegated or prohibited. Which is tautological.
The States battled over the wording of each amendment. Many of the debate texts and the notes from the Founders are still available. How an attorney with the Internet at his fingertips could maintain a contrary delusion is really disturbing to me.
There were no throwaway/meaningless amendments in the Bill of Rights.
The Tenth Amendment means exactly what it says it means. The States barely allowed the Federal Government to have any power under the Articles of Confederation. The Constitution was an effort to allow more power to the Federal Government, but certainly not limitless arbitrary powers... thus the Ninth and Tenth Amendments.
The federal government would not have unlimited power without the 9th and 10th amendments--the rest of the Constitution explicitly limits it to the enumerated powers and those necessary and proper to carry out the enumerated powers. Which is precisely what makes the 10th amendment a tautology--it doesn't disallow any federal action that isn't otherwise disallowed.
Conceptually, how the Constitution works is as follows. The states inherited the sovereignty and unlimited power of the British parliament. In aggreeing to the Constitution, the states delegated some of that power to the federal government, and agreed to refrain from the exercise of certain other powers. The clauses of the Constitution outline the powers delegated and prohibited. All the 10th amendment says is that anything that hasn't been delegated or prohibited hasn't been delegated or prohibited. Which is tautological.
The mere face of the text cannot support an interpretation that the 10th amendment does anything other than state the obvious. If a federal action is otherwise Constitutional, by virtue of falling into one of the delegations, then it is by definition something that has not been reserved to the state.