When Siskiyou County Sheriff Jon Lopey wrote U.S. Attorney General Jeff Sessions in September requesting federal help to fight rampant illicit marijuana cultivation in his vast, rural Northern California county, he wasn't expecting a written reply. Indeed, Sessions didn't write back.

Instead, as if in answer to the prayers of county sheriffs throughout rural Northern California, Sessions rescinded the so-called Cole Memo last week. The 2013 Obama-era directive "advised" federal prosecutors to refrain from prosecuting individuals in the 29 states (and counting) that have decriminalized marijuana, as long as those individuals were in strict compliance with state and local regulations and met certain federal criteria.

Now, the U.S. Department of Justice under Sessions has thrown all that out.

"Given the Department's well-established principles, previous guidance specific to marijuana enforcement is unnecessary and rescinded, effective immediately," Sessions stated in the new directive. This potentially opens the door for federal prosecutors to go after any marijuana business in the country — even in states where it has been decriminalized — since all are in violation of federal law.

Lopey was elated at the attorney general's move.

"I didn't get a direct response to my letter," Lopey said in a telephone interview. "But I think this was a response, to letters like mine [from other rural law enforcement officials in the state]. I'm anticipating there will be more funding available."

Sessions' announcement came just days after California's legal recreational marijuana market opened for business on Jan. 1. Adults 21 and over may now purchase purchase cannabis products across the counter from state-licensed businesses, provided they live in a county or city that allows such businesses.

It's still early days in the state's recreational marijuana industry, but a large number of counties and cities, especially in rural areas, are choosing not to participate in the legal pot boom.

One reason why? Even as proponents celebrate yet another victory in their quest to decriminalize marijuana — in this case the Adult Use of Marijuana Act, Prop. 64, passed by California voters in 2016 and now in full effect — there's been a corresponding "green rush" of would-be entrepreneurs eager to get in on the burgeoning industry and willing to completely skirt local, state and federal laws in order to do so.

In Siskiyou County, where Lopey estimates there are 2,000 illicit cannabis grows on private property and an unknown number of large Mexican drug cartel grows on state and federal public lands, the board of supervisors declared a "state of emergency" in September.

"This has nothing to do with recreational or medical marijuana," Lopey said. "There are millions of dollars to be made in the illicit marijuana drug trade, it's going back east [to states where marijuana fetches a higher price]. They're manufacturing, they're transporting, and it's still against the law to be involved in those activities."

As Sessions pointed out when rescinding the Cole Memo, the cultivation, distribution and possession of marijuana in just about any way, shape or form is prohibited by federal law under the Controlled Substances Act, which only Congress can change. Marijuana is classified as a Schedule I drug, along with narcotics such as heroin and hallucinogens like LSD. In addition, Sessions noted that marijuana trafficking is associated with money laundering, tax evasion and other financial crimes.

This places legislators and law enforcement officials in states that have decriminalized marijuana seemingly at odds with federal law — which in reality has been the case all along, Cole Memo or not. In response to Sessions, California Attorney General Xavier Becerra rushed to defend the state's nascent recreational marijuana industry, which is projected to bring in $1 billion in tax revenue and licensing fees in 2018.

"In California, we decided it was best to regulate, not criminalize, cannabis," Becerra told LA Weekly. "Unlike others, we embrace, not fear, change. After all, this is 2018, not the 20th century. At the California Department of Justice, we intend to vigorously enforce our state's laws and protect our state's interests."

Nevertheless, as the top elected law enforcement official in California, Becerra oversees the state's participation in the Campaign Against Marijuana Planting (CAMP), the multiagency task force comprised of literally thousands of local, state and federal law enforcement officers who have been battling illicit marijuana growers in California since 1983. CAMP and other task forces have been active in California for decades and remain so.

The tug of war between federal and state law began in earnest with the passage of Prop. 215, the Compassionate Use Act, in 1996. People flocked to Northern California, a region already renown for its illegal cannabis, in the first of many "green rushes" that have followed in the wake of decriminalization.

In many cases, the Cole Memo hasn't hindered CAMP and other multiagency task forces from acting, because a certain percentage of these would-be millionaires — and the cartels, of course —don't follow any laws, local, state, or federal.

The Siskiyou County Supervisors' declaration of a "state of emergency" was designed in part to provoke a response from Gov. Jerry Brown, a longtime supporter of decriminalization and the bane of many rural conservatives. But Lopey admits that Brown's Department of Justice has provided Siskiyou County with "incredible support" in the fight against illicit marijuana cultivation.

Even though he's a fervent supporter of state's rights, Lopey said he'll take all the federal help he can get in the case of illicit marijuana.

He can recite an alphabet soup litany of agency acronyms — including the U.S. DOJ, DEA, FBI and HIDTA (High Intensity Drug Trafficking Areas program) — that have provided Siskiyou County with assistance. He gives the state DOJ, the California Highway Patrol, and law enforcement officers drawn from Northern California counties and cities for task forces due credit as well.

Such assistance proved instrumental last May after a local man and woman allegedly offered Lopey a $1 million bribe to provide protection to their proposed nationwide pot-trafficking operation. Lopey contacted the DOJ, the FBI and the DEA instead, and a multiagency task force comprised of federal, state and local law enforcement officials ran a sting operation on the pair, who were arrested in August.

The couple are due to appear in the U.S. Court for the Eastern District of California in Sacramento in February, on charges that include bribery of a public official, conspiracy to manufacture marijuana and manufacturing marijuana. There, they'll face a U.S. Attorney's office led by newly appointed head attorney McGregor Scott, who during a past stint with the district was noted for prosecuting medical marijuana businesses, often using federal law.

Asked to comment on whether Sessions' decision to rescind the Cole Memo would affect how the Eastern District prosecutes marijuana cases, Scott spokesperson Lauren Horwood offered the following response:

"The cultivation, distribution and possession of marijuana has long been and remains a violation of federal law for all purposes. We will evaluate violations of those laws in accordance with our district's federal law enforcement priorities and resources. We will continue our long-standing efforts to assess and address the unique threats and challenges facing our district together with our state, local and federal law enforcement partners."

The Eastern District covers the vast swath of rural inland California from the north to the south, including the Central Valley. Siskiyou County is the fifth-largest out of the state's 58 counties with a population of just 45,000.

Lopey says the county's low real estate prices and accessible water resources have spurred the green rush, to the detriment of local watersheds. Hillsides are eroded and streams are sucked dry and/or poisoned, along with adjacent wildlife, by highly toxic pesticides and herbicides used by illicit growers to bump up crop yields.

This contaminated weed, Lopey notes, winds up in both the state's legal marijuana market and is exported out of state illegally, to be consumed by unwitting customers.

Lopey is a diehard opponent of marijuana for anything but limited medical use, such as patients with seizure disorders. He also refutes the claims of proponents that marijuana is harmless, especially in the case of younger users, and can cite numerous studies supporting his position.

The problem for both opponents and proponents in that debate remains the paucity of such studies, since marijuana's classification as a Schedule I drug strictly limits its use in scientific research, at least in the United States.

While Lopey's general sentiments are shared by most of California's law enforcement community, some public officials are embracing marijuana, or at least the tax revenue from it, as necessary relief for strapped budgets. Humboldt County, just one county to the west from Siskiyou County and one-third of the Emerald Triangle, is now enjoying the fruits of its once-infamous status, as adult customers flock to purchase now-legal recreational marijuana.

In California, the decriminalization of marijuana is unfolding in an era of dramatic criminal justice reform, which began a decade ago after overcrowding conditions in the state's prison system were deemed unconstitutional under the 8th Amendment by a panel of three federal judges. One goal of marijuana proponents and criminal justice reformers alike has been to reduce and in some cases eliminate criminal penalties in marijuana cases in which otherwise no serious or violent crime was committed.

Another major driver of the criminal justice reform has been the fact that blacks and Latinos, most of whom live in or around urban areas, have historically been convicted for nonviolent marijuana infractions at a disproportionate rate when compared to whites. Another factor is the growing recognition among law enforcement, as measured by the respected Pew Research Center, that marijuana isn't as problematic as heroin, cocaine and methamphetamine and shouldn't be penalized as such.

Ashley Bargenquast is an attorney for Bay Area-based law firm Tully & Weiss, which for the past several years has successfully defended numerous northern California clients charged with violations of the state's complex medical marijuana laws. Thanks to the state's new recreational regulations, Tully & Weiss stand poised to continue their winning streak.

"With the passage of Prop. 64, an entirely new avenue for dismissal was created," she explained. "This code section allows any individual previously convicted or facing felony charges for behavior that is now lawful to have their case redesignated as a misdemeanor and possibly even dismissed with the records sealed."

Bargenquast said the burden is now on local district attorneys, who have to show that an infraction committed in the past is illegal under present law. Tully & Weiss intends to hold them to that burden, she said.

"There are countless victims of the war on drugs who can finally have their records cleared for behavior that should never have been a crime in the first place," she said.

As far as state laws are concerned, state Attorney General Becerra has indicated he will go as far as defending any legitimate business owner in legal compliance with the state's new regulations against potential federal prosecution. Now that Sessions has muddied the waters by rescinding the Cole Memo, Bargenquast is concerned that businesses in compliance with state law may be wrongfully accused simply because police are uncertain about the new regulations.

"I think the biggest issue is going to be law enforcement simply not knowing the law," she said. "For example, collectives and cooperatives [medical marijuana producers and retailers, some of whom also form the base of the new recreational industry] are still allowed to operate in compliance with Prop 215 and SB 420 until December of 2018 [the state medical marijuana regulations]. However, I am sure that many collectives will be prosecuted based solely on their lack of a state license."

For his part, Loney said he doesn't go after individuals who are growing three or four plants in their backyard, in compliance with state law, if not the county's ban on outdoor cultivation. He's targeting his limited resources at the larger grows with hundreds and sometimes thousands of plants on private land, and tens of thousands of plants on public lands, where the cartels prefer to operate.

Last year, Lopey says 28,000 plants were eradicated by drug task forces on private land in Siskiyou County, along with 17,000 pounds of processed marijuana. He estimates that accounts for perhaps up to 15 percent of the illegal activity on private land. Another 166,000 plants were eradicated on public lands, accounting for an estimated 25 percent of the criminal activity on public lands.

So will California be able to properly regulate the marijuana market?

"No, I don't believe so," Loney said. "I think some people are going to make a lot of money, but unless you put substantial resources into the regulatory scheme, you can't do it. We quite frankly trusted the marijuana industry too much. They said they would keep the illegal growers out. They didn't. They either were not willing or lacked the ability."

In the meantime, Lopey is hopeful that more federal resources will be at his disposal now that Sessions has rescinded the Cole Memo.

"It's going to be a tough ride for California," he said. "I fully endorse his decision."