By Daniel Kelley

PHILADELPHIA, Aug 21 (Reuters) - You still can't say "marijuana" in the head shop.

For years, the stores that sell marijuana pipes and bongs have insisted that the products they sell are for tobacco use, choosing their words carefully to avoid being ensnared in laws against marijuana paraphernalia.

As states and cities across the country have lowered the penalties for possession, a patchwork of federal, state and local laws means little has changed at the head shops.

"The map of the United States is colorful as to where you can lawfully buy paraphernalia and not use magic code words," said Allen St. Pierre, executive director of the National Organization for the Reform of Marijuana Laws.

Seventeen states have decriminalized marijuana - meaning that possession, but usually not the sale - of small amounts leads to a minor fine and no criminal record. Four states - Washington, Colorado, Alaska and Oregon - along with the District of Columbia, have legalized marijuana, meaning that there is a state-approved marketplace for pot.

In Philadelphia, lawmakers decriminalized possession of less than 30 grams of marijuana - about an ounce - in October 2014, meaning that a person with a small amount gets a fine rather than being hauled away in handcuffs.

But at Wonderland, a head shop festooned with Grateful Dead iconography, the mere mention of marijuana is enough for clerks to refuse a sale.

"Even the mention of medical marijuana means I cannot sell anything to you," said a clerk at the store, before declining further comment and refusing to identify an owner or manager.

That situation is ironic but not surprising to Philadelphia marijuana activist N.A. Poe, who in June led a protest featuring hundreds of people smoking marijuana.

"Before we did that protest, we went and sat down with civil affairs, told them what we were going to do," Poe said, referring to the Philadelphia Police Department's Civil Affairs Unit. "And then we marched down Market Street with a police escort."

Which is to say that it is possible to smoke marijuana in front of the police, even though one cannot in many locales discuss weed in certain stores.

Experts say prosecution for marijuana paraphernalia alone are fairly uncommon.

Many people interviewed for this story, however, point to a 2003 DEA sting called Operation Pipe Dreams, which ensnared 55 people for distributing drug paraphernalia, including actor Tommy Chong, one half of the stoner comedy duo Cheech and Chong. He pleaded guilty and served nine months in prison for selling the "Chong Bong," which was delivered to an undercover business in the Pittsburgh area.

Even in places where possession of small amounts of marijuana is decriminalized for individual tokers, paraphernalia laws may still apply.

In Maryland, lawmakers decriminalized possession of marijuana in 2014. Aficionados caught with less than 10 grams pay a $100 civil fine.

But possession of a pipe with marijuana residue could lead to a $500 fine and a criminal record. A measure that would have decriminalized marijuana pipes and bongs in the state was vetoed in April by Governor Larry Hogan, who said cited concerns that the bill did nothing to prevent driving under the influence.

The legalization of pot in the District of Columbia has completely changed the conversation there, said Adam Eidinger, the owner of Capitol Hemp in Washington, D.C. Police raided the shop in 2011.

Just a few years ago, Eidinger was forced at least once a day to eject patrons of his pot accessories store who uttered the forbidden "M" word. He even tried playing loud music in the shop to thwart surveillance by police.

"We sold pipes for marijuana, but if you mentioned marijuana, I'd tell you to leave, even though I knew - and the owner of every head shop knows - that every single pipe we sold was going to be used for marijuana," Eidinger said.

After closing the store in 2012, he was able to re-open it about two weeks ago after leading a campaign to legalize pot in the nation's capitol city.

"It changes the dynamic you have with your customers when they can say what they want without you having to worry about getting your business shut down," Eidinger said. (Editing by Barbara Goldberg and Dan Grebler)

Our Standards: The Thomson Reuters Trust Principles.