Apparently, the connection between federalism and rolling back the New Deal is an even straighter line than I thought it was:

States’ rights conservatives have always been nostalgic for the pre-1937 doctrines, which they have lately taken to calling the Constitution-in-Exile. They argue — at conferences like “Rolling Back the New Deal” and in papers like “Was the New Deal Constitutional?” — that Congress lacks the power to do things like forcing employers to participate in Social Security. Given how entrenched New Deal programs have become in more than half a century, these plans for reversing history have always seemed more than a bit quixotic.

But that may be about to change. . . .[T]wo Californians who use marijuana for medical reasons argued that Congress, which passed the Controlled Substances Act, did not have the constitutional power to stop them. To pass a law, Congress needs a constitutional hook, and the Controlled Substances Act relied on one of the most important ones, the Commerce Clause, which authorizes Congress to “regulate Commerce . . . among the several States.” The Californians argued that their marijuana did not involve interstate commerce because it never left their state.

That is where Wickard v. Filburn comes in. Roscoe Filburn was a farmer who argued that his wheat crop should not fall under federal production quotas because much of it was consumed on his own farm. The Supreme Court held that even if that wheat did not enter interstate commerce, wheat grown for use on a farm altered supply and demand in the national market. The decision gave Congress broad power to regulate things that are located in one state, like factories and employer-employee relationships.

Some leading conservatives want the court to overturn Wickard and replace it with a pair of decisions from the 1800's that one brief filed in the case said would return “Commerce Clause jurisprudence to its settled limits prior to the New Deal.” . . .

If the Supreme Court drifts rightward in the next four years, as seems likely, it could not only roll back Congress’s Commerce Clause powers, but also revive other dangerous doctrines. Before 1937, the court invoked “liberty of contract” to strike down a Nebraska law regulating the weight of bread loaves, which kept buyers from being cheated, and a New York law setting a maximum 10-hour workday. Randy Barnett, the law professor who represented the medical marijuana users, argues in a new book that minimum wage laws infringe on “the fundamental natural right of freedom of contract.”

In pre-1937 America, workers were exploited, factories were free to pollute, and old people were generally poor when they retired. This is not an agenda the public would be likely to sign onto today if it were debated in an election. But conservatives, who like to complain about activist liberal judges, could achieve their anti-New Deal agenda through judicial activism on the right. Judges could use the so-called Constitution-in-Exile to declare laws on workplace safety, environmental protection and civil rights unconstitutional.

Getting rid of Wickard would be an important first step.

— Adam Cohen, “What's New in the Legal World? A Growing Campaign to Undo the New Deal”, New York Times, 14 December 2004

Note that it’s not just the same legal issues that connect states’ rights on medical marijuana to the New Deal — it’s the same lawyers.