Since it’s inception as a nation, the United States federal government has been engaged in a proverbial ‘tug of war’ with individual states’ rights, with arguments spanning a wide array of legal and social issues.

In the 21st century, one of the most recurring ‘flashpoints’ for the push and pull between federal and state laws is the legalization of marijuana. As a growing number of states pass their own laws legalizing marijuana for medical or personal use—or both—the federal government has remained firmly encamped in the legal belief that marijuana is, and should remain, illegal; indeed, in August, the federal Food and Drug Administration (FDA) rejected states’ efforts to reclassify marijuana from its status as a “Schedule 1” drug under the Controlled Substances Act (CSA). As a result, at least as seen through the eyes of federal law enforcement, marijuana remains as equally ‘illegal’ a substance as heroin or LSD.

For US businesses, particularly those operating in states that have either decriminalized—or even legalized—the use of marijuana, the divergence between state and federal ‘pot laws’ presents a host of potential problems.

Unlike 15 or 20 years ago, when very few states allowed residents to use medical marijuana, today more than 40 states and—ironically, even the District of Columbia–now allow for some form of medical marijuana use. And in the wake of the FDA decision to keep marijuana as a Schedule 1 drug, there will also be a new Administration in Washington as of January—and the man nominated to oversee federal law enforcement has, in the past, stated his strong opposition to any attempts to decriminalize marijuana; should he be confirmed by the Senate, Attorney General-designate Jeff Sessions’ track record indicates he is unlikely to be open to ‘easing up’ on federal enforcement of marijuana laws.

Meanwhile, the gulf between state and federal marijuana laws seems to only be broadening; in the November 8th election, four additional states—California, Nevada, Maine and Massachusetts—joined the list of states making ‘recreational’ marijuana legally available for adults over 21 years of age.

So, what do all these divergent state and federal laws mean for employers and their employees? A great deal depends on who is being asked that question.

Some attorneys are quick to point out that—regardless of what any individual state law may say—federal laws still apply in all 50 states, and marijuana remains a highly illegal drug in the eyes of federal authorities. Still, other attorneys—particularly those assisting businesses hoping to establish themselves within the burgeoning ‘pot dispensary’ or manufacturing markets—argue that their clients are well within their states’ rights to own and operate marijuana-related businesses.

Meanwhile, doctors who might wish to prescribe medical marijuana to a patient in states where it is now permitted, have to pause and wonder whether doing so might put their medical practice at risk—given existing federal laws.

And, for now, it’s those federal marijuana laws that also seem to be dictating the way most employers continue to view–and treat—marijuana, at least in the workplace.

For many companies, regardless of their location or that state’s individual marijuana laws, employees are simply not permitted to show up for work intoxicated—whether as a result of alcohol or any controlled, illegal substance.

In fact, even some states that have chosen to legalize marijuana, have gone out of their way to make it abundantly clear that new marijuana laws should not be interpreted as license to smoke before, or during, workplace hours. In Massachusetts, for example, the state’s marijuana law includes language stating that “the authority of employers to enact and enforce workplace policies restricting the consumption of marijuana by employees” is not changed.

Eventually, all 50 states will have to work cooperatively with the federal government to enact a reasonable—and singular—policy governing the use of marijuana. Until that happens, however, it seems inevitable that marijuana will remain at the center of a political tug of war between authorities in the nation’s capital, and their state counterparts nationwide.