Marijuana is on fire.

Recreational pot is now legal in eight states plus the District of Columbia. Another 20 states allow cannabis for medical purposes.

Five years after Washington and Colorado kicked off the recreational pot craze, lawyers and law students are getting their first casebook on the law and policy of marijuana.

Robert Mikos, a professor at Vanderbilt University Law School who has taught a class on the topic since 2015, this month published “Marijuana Law, Policy, and Authority”—a nearly 800-page tome that explores different approaches to cannabis regulation at federal, state and local levels. Mikos delves into prohibitions and regulations placed on marijuana users, suppliers and third parties, and looks at research of differing pot policies and their implications.

It’s a fertile topic: More and more states are embracing legal pot, but cannabis remains banned under federal law. That conflict creates plenty of questions for law to grapple with.

Vanderbilt Law Professor Robert Mikos

“There’s a need for something that helps lawyers and lawmakers to make sense of all these developments,” Mikos said.

Yet the sheer scope of legal areas that marijuana law and policy touch on—from federalism and criminal law to separation of powers—may have dissuaded others from even attempting a casebook on the topic, he added. Mikos has been studying marijuana law for 10 years and spent the past three years researching and compiling the casebook.

He read thousands of cases in order to find those that best illustrate where laws are alike and where they diverge.

To take an example from the book: How do medical marijuana laws impact search and seizure rules? Both Arizona and Massachusetts allow medical marijuana, yet courts in Arizona have ruled that the scent of marijuana detected during a traffic stop is grounds for police to search a vehicle. Not so in Massachusetts, where courts reached the opposite conclusion, Mikos said.

That marijuana laws are evolving so quickly presents yet another challenge to lawyers practicing in the space, as well as someone trying to write a casebook about it. Mikos said he plans to launch a website that will keep readers abreast of all the latest developments so they won’t have to wait around for a casebook supplement.

Meanwhile, Mikos identified some larger legal and policy patterns among states that are allowing marijuana in some form, which adds some predictability to the seemingly chaotic world of pot law. Steps that California took 20 years ago when it first allowed medical marijuana are likely to be repeated elsewhere, he notes.

There’s clearly an appetite among legal educators and law students for information about the rapidly evolving world of marijuana law and policy. Criminal law and constitutional law courses often touch on the subject, but in 2013, Ohio State University Michael E. Moritz College of Law and South Texas College of Law—Houston both offered the first classes centered on marijuana policy. Mikos estimates that about 30 law schools now offer a course on the topic.