"The Healthnut" wore a baseball cap when he walked into a suburban Denver post office with packages intended for New York and Texas.

Stephen Anderson didn't know it, but he was being watched – with his beard and bumper-less SUV matching the description of a suspect who weeks earlier had shipped marijuana concentrates sniffed out by a drug dog.

After the Texas transplant paid in cash to ship two packages bearing his trade name, search warrant-armed authorities opened them and found more pot concentrates. An inbound package from New York contained $1,960 in cash.

A search of Anderson's home revealed 72 pot plants – well above Colorado’s six-per-person limit – and extraction equipment. Postal surveillance footage showed he had recently shipped items to Ohio and Maryland.

The pot mail bust – which last month saw Anderson sentenced to a year and a day in prison – was one of the first of fiscal 2016, which began in October 2015 and saw an uptick in the number of marijuana packages detected in the U.S. mail system.

The significant 18.4 percent increase in intercepted marijuana packages comes after two years of declines that appeared to dash expectations of doom among pot legalization opponents. Non-marijuana drug mail, by contrast, increased 11.6 percent last year.

Colorado and Washington opened recreational pot stores in fiscal 2014. Steven Nelson/USN&WR

The latest annual numbers come at a sensitive time for the cannabis industry. Federal law continues to ban almost all pot possession, and recent comments from White House spokesman Sean Spicer and Attorney General Jeff Sessions have aroused fear that the Trump administration may abandon the Obama-era approach of empowering states to pursue their own policies.

But analyzing the meaning of the drug mail numbers and their connection to state-level marijuana legalization is tricky. The figures include packages that originate overseas, and the U.S. Postal Inspection Service hasn’t tracked statistics on states of origin.

Also clouding analysis is the fact that conduct such as Anderson’s remains clearly illegal and arguably is unrelated to local laws. Unlicensed and interstate sales aren’t allowed in states with recreational stores, and shipping pot through the mail remains a federal crime.

Cutting against the legal-pot explanation is the fact that intercepts fell the previous two years, during which stores were open in Colorado and Washington. Fiscal 2016 only added Oregon to the list of states with recreational stores (Alaska opened its first shop a month later).

A spokesman for the inspection service says the increase in intercepts can be attributed to better detection tactics and stronger relationships with other federal law enforcement agencies.

“As we continue to develop and improve our use of intel and analytics through these partnerships, we expect we will see more variability in our numbers going forward – not due to increased trafficking by criminals, necessarily, but due to improved detection methodologies,” spokesman Paul Krenn says.

Although the overall number of pot parcel intercepts increased, other downward trends held steady in data provided in response to a Freedom of Information Act request.

The number of actual arrests for mailing controlled substances – for either marijuana or non-pot drug mail – fell for a second year, dropping 4 percent to 1,850.

And the average weight of pot mail continued a long-running drop since at least fiscal 2012, which ended just before voters in Colorado and Washington passed legal pot initiatives. The average pot package weighed a hair under 4 pounds last year, down from 5.5 pounds in fiscal 2012.

Recreational pot initiatives passed in fiscal 2013 in Colorado and Washington. Steven Nelson/USN&WR

The declining average weight could signify more small shipments or simply more diligence from authorities. Explanations could also include an increase in potent concentrates and extracts that can be added to edible products or “vape pens.”

John Rooney, who led counter-narcotics efforts for postal inspectors in Philadelphia before retiring in 2001, believes it's possible that big-time distributors are shipping smaller amounts to avoid attracting attention.

“We wouldn't do anything less than 10 pounds because it wasn’t worth our time” in the mid-1990s, he says, putting downward pressure on the package weights.

Rooney, who says identifying and disabling organizations is the best way to reduce drug mail, believes annual numbers may fluctuate with resources and department priorities. He suspects fewer arrests amid an uptick in intercepts means investigations are lacking.

Krenn says, however, the service is increasing its focus on disrupting international trafficking groups.

Anecdotal information gleaned from local busts reveals a variety of states of origin for marijuana mail last year.

In one two-week drug mail crackdown called Operation Pandora’s Box, the U.S. Postal Inspection Service in central New York, with local help, nabbed 18 people on marijuana charges, with packages coming from a half-dozen states with diverse cannabis laws.

The city of Kenner, near New Orleans, saw a string of at least four marijuana mail busts in early 2016. Two of the busts had the same reported weight, 5.6 pounds. A sergeant for the local police department, which supported postal inspectors, reviewed one of the case files and said California was the state of origin.

People who ship drug mail often prefer the U.S. Postal Service over commercial carriers like Fed Ex and UPS because of the clear warrant requirement protecting packages from whimsical inspection.

Rooney, who says the West Coast historically has been a major source of marijuana mail, found many shippers spread risk among multiple delivery services. Postal inspectors sometimes engage commercial services in making controlled deliveries and arrests.

Eighteen people were hit with pot charges in central New York as part of Operation Pandora's Box. Some also were accused of non-marijuana crimes. (New York State Police)

Though the precise reason for the uptick in intercepts is unclear, some observers view the increase as an indication that regulating pot sales has been a failure.

"Despite promises made by the marijuana legalization lobby, the black market for marijuana continues to thrive," says Kevin Sabet, a former presidential drug policy adviser who has coordinated national anti-legalization efforts through the group Smart Approaches to Marijuana.

"This is the latest evidence to emerge demonstrating that this is not an issue of states' rights or individual freedom, but an issue of public health and safety that cannot be contained within geographic borders," he says. "The promise of a controlled, regulated market has failed to materialize."

But Mason Tvert, a leader of Colorado's legalization campaign and a spokesman for the pro-legalization Marijuana Policy Project, stresses that the overall weight remains lower than before retail stores opened.

And Tvert points out other statistics show declining marijuana intercepts by law enforcement in some Colorado-neighboring jurisdictions and along the U.S. border, where blocked imports from primarily Mexican drug cartels dwarf detected pot mail.

Border agents are intercepting far less marijuana along the U.S. border. Steven Nelson/USN&WR

The amount of pot found in U.S. mail is much less than seized at the border. Steven Nelson/USN&WR

In fiscal 2016, the U.S. Border Patrol seized 1.3 million pounds of pot, half the amount it seized three years earlier. The most recent statistics from the Drug Enforcement Administration show about 160,000 pounds in pot seizures in 2014, down 90 percent from 2010 amid a sea change in state laws.

By contrast, postal inspectors took 36,642 pounds of pot last year, less than in the year before the Colorado and Washington votes.

"It appears less marijuana was distributed through the mail last year than in the years before Colorado legalized and regulated marijuana for adult use," Tvert says.