By Geoffrey G. Slaughter

Under our Constitution, federal law is “the supreme law of the land.”

State laws at odds with federal law are invalid. Although federal supremacy has prevailed for more than 225 years, it was a hotly contested topic among the founding generation. Specific applications of federal law have been highly controversial throughout our history and remain so today.

The Articles of Confederation, our nation’s first governing document, had no analogous provision.

Under the articles, various state laws often conflicted with national law. Those conflicts, in part, prompted the Constitutional Convention in the summer of 1787. Delegates to the Philadelphia convention initially considered amending the articles but soon abandoned them in favor of a new charter.

When the convention adjourned in September 1787, the proposed Supremacy Clause became a “source of much virulent invective and petulant declamation.”

Not only was the clause a dramatic departure from the status quo, but it tapped into deep divisions within our fledgling nation. Federalists advocated for a strong, centralized national government. Anti-federalists, meanwhile, urged that state governments be strong and the national government weak.

During the state ratifying debates, Federalists successfully defended inclusion of the Supremacy Clause in the adopted Constitution. They believed that without a Supremacy Clause the new Constitution “would have been evidently and radically defective.”

James Madison likened a centralized federal government subject to various state laws to “a monster, in which the head was under the direction of the members.”

Despite the general consensus that federal law is supreme, there have been various challenges to the supremacy of federal law throughout our history. States have sometimes tried to prevent the federal government from enforcing those aspects of federal law the states believed to be unconstitutional.

Examples include legal challenges to the Fugitive Slave Act of 1850, open defiance of the Supreme Court’s school-desegregation rulings of the 1950s and, most recently, an unwillingness to accept certain features of the Affordable Care Act — Obamacare — even after the Supreme Court upheld their legality.

In 1958 the Supreme Court squarely held in Cooper v. Aaron that state efforts to ignore federal law must fail. States, according to the court, are bound by Supreme Court decisions and must enforce them even if they disagree with them.

Some prominent dissenting voices, including Reagan-era Attorney General Edwin Meese, have taken issue with Cooper. These objectors agree the Constitution is the supreme law of the land.

But they disagree that the Supreme Court’s interpretative rulings are supreme. According to Meese, “[e]ach of the three coordinate branches of government created and empowered by the Constitution – the executive and legislative no less than the judicial – has a duty to interpret the Constitution in the performance of its official functions.”

President Obama’s administration may seem an unlikely voice on this subject, given its belief in a vigorous federal role in many areas of governance. But the Obama Justice Department has taken an unmistakable hands-off view when it comes to enforcing federal drug laws.

The Controlled Substances Act classifies marijuana as a Schedule 1 substance and makes it a federal crime to possess, cultivate, or use marijuana.

In 2005, the Supreme Court held in Gonzales v. Raich that federal laws criminalizing marijuana are a permissible exercise of Congress’s commerce power. According to the court, “[t]he Supremacy Clause unambiguously provides that if there is any conflict between federal and state law, federal law shall prevail.”

Yet the Department of Justice’s current policy is to treat the enforcement and prosecution of federal marijuana laws as a low priority. Following November’s general election, eight states and the District of Columbia have now legalized the recreational use of marijuana.

Another 20 states have legalized marijuana use for medicinal purposes. These 29 state (or District of Columbia) laws stand in direct defiance of federal law. The non-enforcement of these federal laws has effectively legalized marijuana in a majority of states.

It remains to be seen whether the Trump administration will reassert the supremacy of federal drug laws by cracking down on marijuana distribution and consumption in non-compliant states. Should the national government resume enforcing marijuana prohibitions, the Supremacy Clause will play a central role in the legal arguments and analysis.

Justice Geoffrey G. Slaughter is a member of the Indiana Supreme Court and the immediate past president of the Indiana Bar Foundation. Send comments to [email protected].