Santa Rosa detectives were surfing Craigslist one day when they came across a "for sale" posting that caught their attention.

Someone was offering top-shelf marijuana — described as "crystal-laden" and "very distinctly scented" — for $2,700 a pound.

The post came under a banner citing Prop. 215, the voter-approved initiative allowing Californians with a doctor's recommendation to possess and use pot.

"If you're looking for the best, don't waste your time on cheaper meds," read the ad, which was accompanied by a picture of the greenish weed and a phone number.

Undercover officers didn't hesitate to call the number. They set up a purchase April 11 in the Santa Rosa Avenue Target store parking lot, where they arrested Krish Singh, 43, of Rohnert Park.

Despite his insistence that the weed in his orange Camaro was intended for qualified patients, Singh was charged with felony possession for sale and faces prison if convicted at his Aug. 31 trial.

Singh is believed to be just one of hundreds of people who are selling marijuana on Craigslist right next to ads hawking cars, apartment rentals and kitchen appliances.

A quick search of the website Monday showed people selling strains like Presidential Kush and Sour Diesel in quantities ranging from grams to multiple pounds. Postings for hashish are plentiful and there is no shortage of live plants available.

Others were selling medical marijuana cards or looking to buy pot.

Many of the postings specify that the weed will be sold only to patients with doctors' recommendations and then only to members of recognized collectives.

But there is debate about whether such disclaimers make it legal.

Defense lawyers argue it does. Distribution among patients is allowed under the state's Compassionate Use Act and there is no provision against Internet advertising, they say.

"Nothing in state law prohibits this," Santa Rosa attorney Joe Rogoway said. "Provided that both are qualified patients."

But police maintain Craigslist sales are against the law. Marijuana can only be distributed among legitimate care providers or members of a closed collective — and that isn't what's happening, they say.

Further, there are limited circumstances where someone can legally collect money for selling marijuana, said prosecutor Anne Masterson, who handles drug cases for the District Attorney's Office.

Most of the Craigslist ads are posted by drug dealers who are attempting to do business by masquerading as medical marijuana care providers, said Santa Rosa police Sgt. Mike Tosti, who heads the department's narcotics unit.

"Our stance is it absolutely isn't for medical purposes," Tosti said.

He described sales as "rampant" over the past five years. There's so much activity these days that detectives pursue only cases involving large quantities or where someone has lodged a complaint.

"We don't have enough hours in the day to go after every single ad on Craigslist," Tosti said. "It comes down to priority and resources. If something catches our eye we'll look into it."

But whether Sonoma County jurors will convict someone who claims to be providing medical marijuana through Craigslist remains to be seen.

In the Singh case, the defendant had a medical marijuana identification card but undercover police said he didn't ask for theirs. And their conversation was recorded.

Singh's lawyer, Jeff Mitchell, said the outcome could be watched closely.