Denver International Airport will be the first city facility to prohibit marijuana possession on all of its property as it attempts to combat illegal interstate trafficking in the face of federal law.

Airport officials plan to begin enforcing the new policy, which is the furthest-reaching among the city’s marijuana limitations, in early January.

Recently adopted city ordinances ban the display and transfer — but not mere possession — of marijuana on city-owned property including parks, the 16th Street Mall, streets and sidewalks near schools.

“We talked to all of (the federal agencies involved), and they’ve expressed concern for good reason, but it was our decision based on the way the airport operates,” said Stacey Stegman, DIA spokeswoman. “We didn’t want to impact other airports and other agencies, and we didn’t want to facilitate transporting marijuana across state lines.”

Stegman said DIA chose to bar all possession and display of pot to eliminate confusion and make the same rules apply to all. She said the presence of federal agencies at DIA also was a factor; marijuana remains illegal under federal law.

The airport has discretion to set such rules under state law and city charter, said Denver Assistant City Attorney David Broadwell.

“Amendment 64 broadly decriminalized the possession of marijuana, but the caveat is that the owner of a facility can impose special restrictions,” Broadwell said.

The law specifically allows any entity “who occupies, owns or controls a property” to set its own marijuana rules at that property.

Under city charter and laws, the manager of aviation — currently Kim Day — executes control of DIA, Broadwell said.

“They are probably within their rights this time, for once,” said Rob Corry, an outspoken pro-pot lawyer in Denver. “Not the answer I would prefer, but it is what it is.”

The nation’s fifth-busiest airport must walk a fine line as it is owned by a municipality. Yet it must also abide by federal regulations.

“Denver (airport) is a commercial service provider, making it a federally regulated facility,” said Jeffrey Price, an aviation and airport security expert and professor at Metropolitan State University of Denver. “So at the end of the day, the airport is usually going to err on the side of the federal government.”

The U.S. Department of Justice said in August it would not interfere in Colorado’s marijuana legalization except for eight types of violations, including marijuana transferring from a state where it is legal to a state where it is illegal.

After Amendment 64 went into effect, airport visitors could carry an ounce or less at the airport as long as they weren’t going through security, Stegman said. Flying with marijuana — including medical marijuana — is not allowed because pot possession is prohibited by the Transportation Security Administra-tion, she said.

But TSA, a U.S. government agency, says the state’s pot legalization will have no impact its policies or how it will implement security checks at Denver.

TSA’s prohibited items website notes that “TSA officers do not search for marijuana or other drugs; however, if an item is found that may violate federal law during security screening, TSA will refer the matter to law enforcement.”

TSA’s dog unit is only trained to sniff out explosives or safety hazards, Price said, and is not able to detect drugs.

And while the airport has decided to implement a zero-tolerance marijuana policy, it doesn’t plan to actively enforce the policy.

“It’s not like we are going to do checkpoints. We just want people to comply,” Stegman said, noting that a violator would have to be discovered by other means, such as committing a different crime and having pot found in the perpetrator’s possession.

Or, as Price said, if a customs dog walks by and detects pot, a passenger could be nailed.

Stegman said the airport will add decals on sliding glass doors and signs stating the rules on airport property. The signs state: “It is unlawful to possess, consume, use, display, transfer, distribute, sell, transport or grow marijuana in this airport. Violators may be fined up to $999.”

Kristen Leigh Painter: 303-954-1638, kpainter@denverpost.com or twitter.com/kristenpainter