[link|http://a257.g.akamaitech.net/7/257/2422/06jun20051130/www.supremecourtus.gov/opinions/04pdf/03-1454.pdf|The Decision] (79 page .pdf).

There are at least 2 competing constitutional ideas in conflict in this case. There's the [link|http://caselaw.lp.findlaw.com/data/constitution/amendment10/|10th Amendment]:

The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.

Since the Constitution doesn't say anything about medical marijuana, the states should be free to regulate it.

However, the [link|http://caselaw.lp.findlaw.com/data/constitution/article01/28.html|Commerce Clause][1] of [link|http://caselaw.lp.findlaw.com/data/constitution/article01/index.html|Article 1 of the Constitution] says:

Section 8.

The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;

To borrow Money on the credit of the United States;

To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;

To establish an uniform Rule of Naturalization, and uniform Laws on the subject of Bankruptcies throughout the United States;

[...]

The Commerce Clause is what has been used to justify much of the federal regulation in the US, especially since the 1930s. (Link [1] above talks about the Commerce Clause in more detail.) One person's proper regulation to protect health and safety is another person's oppressive boot of the federal government.

In short, the USSC majority held that Congress has the power to regulate marijuana use. And if Congress decides to outlaw its use for medical purposes, then that regulation trumps any state law permitting it.

Footnote 37 of the decision (p.27-28) says:

37 We acknowledge that evidence proffered by respondents in this case regarding the effective medical uses for marijuana, if found credible after trial, would cast serious doubt on the accuracy of the findings that require marijuana to be listed in Schedule I. See, e.g., Institute of Medicine, Marijuana and Medicine: Assessing the Science Base 179 (J. Joy, S. Watson, & J. Benson eds. 1999) (recognizing that \ufffd[s]cientific data indicate the potential therapeutic value of cannabinoid drugs, primarily THC [Tetrahydrocannabinol] for pain relief, control of nausea and vomiting, and appetite stimulation\ufffd); see also Conant v. Walters, 309 F. 3d 629, 640\ufffd643 (CA9 2002) (Kozinski, J., concurring) (chronicling medical studies recognizing valid medical uses for marijuana and its derivatives). But the possibility that the drug may be reclassified in the future has no relevance to the question whether Congress now has the power to regulate its production and distribution. Respondents\ufffd submission, if accepted, would place all homegrown medical substances beyond the reach of Congress\ufffd regulatory jurisdiction.

They argue against the Respondent's submission, saying that if it's accepted (as it was in the dissents), then Congress would have no power to regulate any "homegrown medical substances" - a position they flatly reject.

The majority opinion concludes with (p.33-34 of the .pdf):

Respondents also raise a substantive due process claim and seek to avail themselves of the medical necessity defense. These theories of relief were set forth in their complaint but were not reached by the Court of Appeals. We therefore do not address the question whether judicial relief is available to respondents on these alternative bases. We do note, however, the presence of another avenue of relief. As the Solicitor General confirmed during oral argument, the statute authorizes procedures for the reclassification of Schedule I drugs. But perhaps even more important than these legal avenues is the democratic process, in which the voices of voters allied with these respondents may one day be heard in the halls of Congress.

Under the present state of the law, however, the judgment of the Court of Appeals must be vacated. The case is remanded for further proceedings consistent with this opinion.

It is so ordered.

In this and in many other cases recently, it seems that in order to gain (or regain) liberty that's based on reason and science, it's necessary for us to petition Congress. That's reasonable and proper. But I wonder how much less the 10th Amendment will mean in coming years...

HTH.

Cheers,
Scott.