The conservative right, led by former President Bush, pushed the Supreme Court in 2005 to mandate federal control of marijuana over state sovereignty in a case regarding homegrown marijuana for medical use. They should not have won that but they did. That set the case law for this issue which is the definition of the reach of the federal government's power to regulate commerce.
The 2005 ruling, which conservatives hailed as a huge victory in the War on Drugs at the time and actually asked that the federal government be able to steamroller individual choice and states' rights, was duly handed down. Conservative Justices Antonin Scalia and Anthony M. Kennedy joined a 6-3 ruling that said Congress could regulate marijuana that was neither bought nor sold on the market but merely grown at home legally for sick patients. That enabled the DEA to keep raiding over the wishes of the voters and they are still at it. No one at the time anticipated the passage of a health care bill.
The conservative Supreme court ruled in favor of the conservative position (which was not thought out past the issue at hand) that the Constitution gives Congress nearly unlimited power to regulate the marketplace as part of its authority "to regulate commerce." Bush was pushing for federal control over everything he touched and had a Republican Congress and a Conservative Supreme court behind him.
The conservative Republican base got what they wanted. Federal law trumps states' rights and it is now established in law. President Obama has simply used the same ruling for his own purposes. The Supreme Court is not going to reverse itself because of unintended consequences.
When the case gets back to the Supreme court, I have no doubt that Justice Scalia will have a kind word for the people who so recently argued the other side of the same issue. The thirteen or fourteen Attorneys General who are bringing this case will surely have the opportunity to explain why they are attempting to challenge the very same law they fought so hard to establish in 2005 and won by a 2-to-1 majority.
The huge irony is that neither a conservative nor a liberal Supreme Court is going to reverse the ruling. If socialism is afoot, George Bush sowed the seeds. He didn't quite understand what tipping the balance of government heavily in favor of the executive branch would do. Now we know.