As of July 1, thanks to a ballot initiative that Maryland voters overwhelmingly approved last November, state law will allow adults 21 or older to publicly possess up to 1.5 ounces of marijuana. In anticipation of that development, Maryland legislators last month passed H.B. 1071, which will bar police, also effective July 1, from treating the smell of cannabis as sufficient grounds for stopping or searching pedestrians or cars.

Virginia enacted a similar law in 2020, and legislators in other states, including Missouri and Illinois, have proposed the same basic reform. The reasoning behind it is straightforward: Once it is legal to possess small amounts of cannabis, an odor indicating the presence of that substance no longer constitutes evidence of a crime. It therefore cannot, by itself, provide reasonable suspicion for a stop or probable cause for a search. Yet the Maryland bill, which the Democrat-controlled legislature approved by a 101–36 vote in the House and a 27–20 vote in the Senate, recently became law without Gov. Wes Moore’s signature, which suggests he had reservations about it.

Moore, a Democrat who took office this year, served on the board of the Chicago-based cannabis company Green Thumb Industries until March 2022 and unsurprisingly supported legalization when he ran for governor. He refuses to explain his reasons for declining to sign H.B. 1071, which in addition to the search-and-seizure provisions reduces the maximum civil fine for public pot smoking from $250 to $50. But the legislative debate about the bill is a window on the perilous police practice of using marijuana possession as a pretext to investigate other crimes and an excuse to seize property.

Under H.B. 1071, “a law enforcement officer may not initiate a stop or a search of a person, a motor vehicle, or a vessel based solely” on “the odor of burnt or unburnt cannabis,” suspected possession of personal-use amounts, or “the presence of cash or currency in proximity to cannabis without further indicia of an intent to distribute.” In the last situation, of course, police would seize the cash along with the cannabis, using it to augment their budgets under civil forfeiture laws, which helps explain why cops are so keen to follow their noses.

If an officer is investigating someone suspected of driving while impaired by marijuana, H.B. 1071 says, he may search only parts of the car that are “readily accessible” to the driver or “reasonably likely to contain evidence” of that offense. Any evidence obtained in violation of the new rules is “not admissible in a trial, a hearing, or any other proceeding.” Notably, that includes “evidence discovered or obtained with consent,” which is little more than a legal fiction when people are waylaid by armed agents of the state with the power to informally punish uncooperative drivers.

Under prior Maryland law, possessing 10 grams or less of marijuana was a civil infraction punishable by a $100 fine. In 2017, the the Maryland Court of Appeals (now the Supreme Court of Maryland) nevertheless held that “a law enforcement officer has probable cause to search a vehicle” when he “detects an odor of marijuana emanating from the vehicle, as marijuana in any amount remains contraband, notwithstanding the decriminalization of possession of less than ten grams.”

Three years later, however, the court ruled that “the mere odor of marijuana alone is not indicative of the amount of marijuana that may be in a person’s possession and does not provide a law enforcement officer with the requisite probable cause to arrest a person and perform a warrantless search of that person incident to the arrest.” In 2022, by contrast, the court said “the odor of marijuana” does provide “reasonable suspicion of criminal activity sufficient to conduct a brief investigatory detention,” overturning a lower court’s contrary ruling.

H.B. 1071 clarifies this confusing situation in light of legalization: It says the smell of marijuana is not enough, by itself, to justify a warrantless search or a stop. Although the logic of that reform seems clear, the bill’s opponents argued that such a categorical rule goes too far. Cops wanted to continue stopping and searching people for marijuana even after they are legally allowed to possess it.

The Maryland Chiefs of Police Association and the Maryland Sheriffs’ Association noted that some marijuana-related conduct will remain illegal in Maryland, including possession by people younger than 21, possession of more than 1.5 ounces, driving under the influence, and unlicensed distribution. Since the smell of pot still could be evidence of a crime, they said, “using odor of cannabis alone as grounds to briefly detain a person or to search a vehicle will not violate the Fourth Amendment and would be reasonable.”

Those police organizations cited a December 2022 report in which Brian Frosh, then Maryland’s attorney general, said “the odor of cannabis will likely still permit a police officer to briefly detain the person to investigate whether they have a criminal amount of cannabis.” Frosh also thought the Maryland Supreme Court probably would conclude that “the odor of cannabis emanating from a vehicle will still justify a police officer’s search of that vehicle” even after legalization of low-level possession.

“We realize it might seem counterintuitive,” Frosh wrote. But “to conduct a search of a vehicle under the Constitution, an officer needs only probable cause to believe that the vehicle contains evidence of a crime, not that a person in the vehicle has committed or is committing a crime.”

You might think that when an officer pulls someone over, smells marijuana, and proceeds to search the car, he is acting on the supposition that the driver has committed a crime. But according to Frosh, that cop is merely thinking he will find “evidence of a crime,” not necessarily a crime that the driver (or a passenger) has committed. If so, who exactly is the suspect?

In any case, probable cause requires “a fair probability that contraband or evidence of a crime will be found in a particular place.” In this context, that probability surely depends on the likelihood that marijuana in a car will exceed 1.5 ounces. After legalization, what percentage of drivers who are transporting marijuana can be expected to have more than the law allows? If that percentage is low, it is hard to see how a search can be justified based on nothing more than the inferred presence of cannabis.

The Colorado Supreme Court rejected that premise in 2019, when it ruled that an “alert” by a drug-sniffing dog trained to detect marijuana as well as other drugs does not provide probable cause for a search. Courts in other states where cannabis is legal have reached similar conclusions, forcing police to retrain or replace their canine narcs. And back in 2015, after Massachusetts had decriminalized marijuana possession but before it legalized recreational use, the state’s Supreme Judicial Court ruled that the smell of burnt marijuana cannot by itself justify a traffic stop.

Rather than wait to see where the Maryland Supreme Court might come down on these questions, state legislators made a policy choice that obviates the need for further litigation and adjudication. And in making that choice, they eliminated one of the many excuses that police use to hassle people who pose no threat to public safety.

This particular excuse can be stretched beyond all credibility. In 2012, for example, The Virginian-Pilot reported that Chesapeake officers “have been pulling over cars on the grounds that they smelled marijuana while cruising down local roadways.” One of those cops explained how that technique supposedly worked: “We drive our patrol car with the vents on, pulling air from the outside in, directly into our faces.”

In 2011, New Jersey cops impounded a BMW based on a purported “strong odor of raw marijuana” and tore it apart over the course of three weeks with the help of drug-sniffing dogs, causing more than $12,000 in damage. They did not find the marijuana they supposedly smelled or any other contraband.

Two years later, after pulling over a car for contested reasons, an Idaho state trooper opened the trunk with the driver’s not-entirely-voluntary consent and, according to the resulting lawsuit, “claimed he could smell the odor of marijuana,” despite “the strong gusts of wind and precipitation that day.” The ensuing search of the car discovered nothing illegal. The driver’s lawyer told The Denver Post his client “does not use marijuana and never has.”

In 2018, the Kansas Supreme Court upheld a warrantless apartment search based on a cop’s claim that she “smelled a strong odor of raw marijuana emanating from the apartment” while standing outside the front door. What police ultimately discovered was 25 grams (less than an ounce) of marijuana, which was inside a sealed plastic container, inside a locked safe, inside a bedroom closet about 30 feet from where the officer had been standing. The cops also found “a small amount of marijuana on a partially burnt cigarillo in the living room,” which would have smelled like burnt marijuana, not “raw marijuana.”

That same year, a Louisville, Kentucky, SWAT team terrorized an innocent family during a fruitless home invasion. The raid was based partly on “a strong smell of fresh marijuana” that a detective claimed to have noticed while standing on the front porch.

I could go on, but you get the idea. Cops, aided by their not-so-trusty dogs, commonly use the real or imagined smell of marijuana to justify outrageous invasions, including futile searches, highway and airport robbery, and roadside sexual assault. The odor of pot even figured in the 2016 death of Minnesota motorist Philando Castile, who was shot by a cop who later said the smell frightened him.

It is bad enough that such things happen in jurisdictions where marijuana remains illegal. It is beyond comprehension that they would continue after a state repeals that prohibition.