'If your life ever gets boring, try this for some excitement—load up your car with live marijuana plants." You might expect Greg Campbell, a former war correspondent whose work inspired the 2006 film "Blood Diamond," to have nerves of steel. But the confusing state of the nation's marijuana laws, which he chronicles in "Pot Inc.," reduces him to quiet panic as he drives through Fort Collins, Colo., where he now lives, carefully coming to a full stop at every stop sign.

The six fledgling pot plants belted into the backseat of his Ford Explorer are as legal as you can get. Mr. Campbell has a doctor's recommendation authorizing him to grow and use marijuana, thanks to a 2000 amendment to the Colorado state constitution and a cottage industry of physicians willing to define "severe pain" expansively. Still, this 40-year-old suburbanite—who is theoretically doing some gardening to relive back pain but actually planning to become a peculiar kind of drug dealer—could, quite possibly, wind up in jail.

Mr. Campbell isn't a smoker. He decides to grow for fun and profit when he finds himself smack in the middle of the Green Rush, a boom in "ganjaprenurialism" that was brought on, in part, by a memo issued by President Barack Obama's then-Deputy Attorney General David Ogden in 2009, stating that U.S. attorneys "should not focus federal resources" on "individuals whose actions are in clear and unambiguous compliance with existing state laws providing for the medical use of marijuana."

Thousands of green-thumbed entrepreneurs leapt into action, taking advantage of often vague laws to sell their product to recognized dispensaries (as Mr. Campbell plans to) or join group enterprises where they get paid to grow for others as designated "caregivers."

But the memo did nothing to change policy, and the Obama administration has actually been more zealous than its predecessors about prosecuting marijuana users, growers and sellers. State leniency means that jail is much less likely—the feds account for less than 1% of marijuana arrests—but far from impossible.

Opponents of medical-marijuana laws argue that the legislation is merely the thin end of the legalization wedge. They're right. Today marijuana is increasingly seen as legitimate medicine, and it is legal for medicinal purposes in 16 states and the District of Columbia. But that's not what the political fight over medical marijuana is primarily about. In 2011, a majority of Americans told Gallup pollsters that they favor legalizing marijuana use across the board.

Public opinion has come a long way since the first great wave of paranoia over "Marihuana" in the 1930s pushed pot into the weeds by imposing a high tax and harsh penalties—or even since Richard Nixon's first term, when the Controlled Substances Act classed marijuana as a Schedule I substance, along with heroin and LSD.

But national legalization remains off the table. Instead, conflicting rules have created a web of technicalities that cause Mr. Campbell to jump every time the doorbell rings. Haunted by the odor of mature plants in his basement, "every Jehovah's Witness or Girl Scout who came calling became a suspected DEA agent or undercover narc." He discusses his crop with clerks in gardening shops but remains worried by the idea of a possible pre-dawn raid on his family's home. One of the achievements of his book is to illustrate how untenable half-measures are in the long run.

In many states, the only unambiguously legitimate course of action requires nauseated cancer and AIDS patients or their overburdened caregivers to grow their own medicine. Meanwhile, a good harvest from his legal plants means that Mr. Campbell is likely to possess, however briefly, more than the two ounces of pot allowed by Colorado law.

Even Denver DEA Special Agent in Charge Jeff Sweetin frets about a legal landscape where impounded plants may be deemed legit: "Do you want to dial 9-1-1 and have the Douglas County Sheriff tell you 'I can't send anybody; all my guys are out watering the plants'?" Nowadays, vindicated growers regularly leave Colorado sheriffs' offices with evidence bags full of weed.

Mr. Campbell wasn't the only one attracted to the skunky scent of a book deal in these exciting times. In "Heart of Dankness," Mark Haskell Smith embarks on a similar journey of discovery, traveling from Amsterdam to Mendocino, Calif., and back again in search of an answer to the question: Why is some weed so awesome, dude?

Cleverly, Mr. Smith has selected a quest that requires him to smoke a great deal of top-of-the-line pot. At the Cannabis Cup, an Olympics-meets-trade-show event in Amsterdam, Mr. Smith probes for an elusive quality—dankness—prized by cannabis connoisseurs, the perfect combination of strong odor, physical beauty, potency and a certain je ne sais quoi.

Mr. Smith comes off as a dilettante, mostly ignoring or mischaracterizing the political and legal landscape he skips across in favor of oenophile-style bloviating about the citrus overtones in "artisanal" Super Lemon Haze. One California vendor speaks fondly of the strain Spruce Sativa Kona because it offers "a linger trickle of joy . . . a pre-psychedelic tickle." But Mr. Smith also captures the rapid professionalization of the industry, from Dutch seed banks to California carpenters advertising a specialty in "grow rooms." That same ticklish vendor tells Mr. Smith: "For me, an enlightened farmer is somebody who knows how to use a liquid chromatography and PCR machine"—serious scientific equipment used to manipulate DNA.

Contrary to what Mr. Smith's book might suggest, today's typical marijuana smoker is not an obsessive connoisseur. Increasingly, indeed, it is someone like Mr. Campbell. After his caper is over, plants harvested and trimmed, product sold to an appreciative Craigslist buyer, grow room defunct, Mr. Campbell—who hasn't smoked since a stretch of persistent and failed experimentation in his college years—settles in to enjoy a joint rolled from a couple of stray buds that escaped during the sorting process. Sitting alone in an Adirondack chair on his own porch, doctor's note in his pocket, he enjoys the fruit of his prodigious labors. "There was no paranoia this time, no worry that someone would appear at my elbow and expect me to answer their questions or to explain myself."

Katherine Mangu-Ward is the managing editor of Reason magazine. This review originally appeared in The Wall Street Journal on April 7, 2012, with the headline "Turning Over a New Leaf."