KNIGHT: Seattle Washington - up on the north-west shoulder of the United States. It was here in the 1980s, that the distinctive local Seattle Sound burst out of bars and clubs and garages and became a global phenomenon. It was the music of alienation and apathy, dislocation and dissatisfaction. They called it grunge.

These days in Seattle, the flannel shirts are ancient history.

MICHAEL BLUE: "Public opinion polls in the US suggested that this was going to move quickly".

KNIGHT: Now if you want to turn the world on its head, make a noise and a whole lot of money - you put on a suit and sell marijuana. Next month Washington State will follow Colorado and become the 2nd state in the US to legalise cannabis. Then chances are, your dope dealer will look like this - young, ambitious and with an Ivy League pedigree.

BRENDAN KENNEDY: "We actually met on the first day out of school at Yale.

KNIGHT: "Did you click straight away?"

MICHAEL BLUE: "We did, we did. We came from very different backgrounds. I came from Arkansas, from a very conservative family in the south. Brendan grew up in San Francisco in an Irish Catholic upbringing".

KNIGHT: Brendan Kennedy and Michael Blue, together with their friend Christian Groh, make up Privateer Holdings. It's the first private equity firm dedicated to cannabis. They're raising money for their own marijuana company and to invest in others, taking advantage of the new laws.

BRENDAN KENNEDY: "I'm not sure I could work in the tobacco industry. I'm not sure I could work in the alcohol industry but we eventually got comfortable with that moral question and in fact, you know today, having talked to so many patients and physicians and talked to so many activists who are interested in individual civil liberties or patient rights, you know we feel this moral imperative to succeed".

KNIGHT: Even before the new laws took shape, Privateer raised seven million dollars from investors. They bought a website called Leafly.com. It was a clever move. Leafly is now the go-to site to search and review hundreds of strains of marijuana. Every day 3,000 consumers are downloading the smartphone app.

BRENDAN KENNEDY: "Fifty-eight percent of Americans believe that cannabis should be legalised for recreational purposes and then eighty-five percent of Americans believe that cannabis should be legal if a doctor has prescribed it and you can't get eight out of ten Americans to agree on anything but they agree on that and that's.... for us that's fascinating".

KNIGHT: Privateer is muscling up for the cannabis boom to come, raising a hundred million dollars for the next investment round. The minimum stake they'll accept - a million dollars.

MICHAEL BLUE: "You know it's a massive industry now and you know it will only grow as further legalisation takes place and you know if you look globally, you know it's a hundred and fifty billion dollar industry. That's the only reason you know why we jumped into the space".

KNIGHT: That space is getting crowded. Privateer got its start in the medical marijuana business. In many states in recent years, it's been possible to get cannabis if you had the right paperwork from a medical professional. Now the medical marijuana sector is worth hundreds of millions of dollars and many of its operators are gearing up for the new legalised boom time.

The state has received 7,000 applications for recreational licences to sell pot and new products are already filling the stores.

This medical marijuana dispensary is one of many owned by a long time marijuana activist, John Davis.

JOHN DAVIS: "This plant was one of the most widely grown things. The first crop in our nation to be grown, it used to be legal currency in the United States at one point in history".

KNIGHT: Now the activist has become corporate evangelist and one of the more strident advocates for mainstreaming marijuana.

JOHN DAVIS: "I don't smoke during the day because I need a clear head, I'm a business guy, but you know this is it. I mean this is, this is what you know all the big deal is about. It's a plant.

In 1937 when it became illegal, cannabis was available at all pharmacies and there were no age restrictions and smoked cannabis was almost unheard of and now, look at the United States. We're awash in cannabis, right? Because we made it illegal and prohibitionist policies simply don't work. We need a smart approach".

KNIGHT: John Davis is now developing a chain of stores, selling his own line of branded, luxury marijuana cigarettes.

JOHN DAVIS: "There's going to be the low market which I have no interest in - the mid-market, and the luxury market. Luxury market seems to be... to me to be a no brainer because I have an excellent cannabis".

KNIGHT: But beyond the product, there's the paraphernalia. Like this marijuana pen that you connect to a computer via USB port. The waxy substance inside is 90% THC, the key chemical that gets you high. The computer heats up the pen and one puff on this is the equivalent of a whole joint.

JOHN DAVIS: "Yeah it's a psycho active substance but compared to alcohol it's nothing. I mean as far as the impact to health, as far as the impact to society. I mean it's really a fairly benign substance".

KNIGHT: Under US federal law all this is still highly illegal, but the White House is telling its federal drug agencies to look the other way and let the states do their thing. Aside from the two States to go fully legal, 18 others have decriminalised cannabis to enable a medical marijuana sector. Once marijuana emerges from a black market, it can be taxed. Revenue in the cannabis states is starting to flow and filling the coffers of depressed economies with money that goes to under-funded public hospitals and schools.

BRENDAN KENNEDY: "In the United States we believe that the cannabis industry is somewhere between 40 and 50 billion and that's made up of medical and then the black market".

KNIGHT: It's a massive market and when the recreational corporates grab their slice of it, it will be with all the sophisticated branding, marketing strategies and signage you'd expect from big retailers.

MICHAEL BLUE: "So our premise is to treat the cannabis industry like any other industry and for so long the branding and marketing in this space has been all about you know using the colour green and putting pot leaves on everything and you know everything has to include tie-dye and it's just... no one is looking at this and treating it like a professional industry and like it should be treated".

KNIGHT: Seattle's marijuana start-ups don't have to look far for model American success stories to inspire them. This city is home to huge global icons like Boeing, the huge web retailer Amazon, and the global coffee-house, Starbucks. Indeed if the pot entrepreneurs have anything to do with it, dope will become as acceptable and accessible as a cup of coffee.

BRENDAN KENNEDY: "There's something to be said about an endeavour like Starbucks that's a company that has taken a product and educated people about coffee and they focus on environmental issues".

KNIGHT: "And they're everywhere".

BRENDAN KENNEDY: "And they're everywhere".

PATRICK KENNEDY: "It's not about your civil liberty and your ability to smoke a joint now and again. This is about a commercial for profit behemoth coming in to prey on your kids, addict them and make money off them at your expense."

KNIGHT: Where there is smoke there is some fiery opposition and we find it on the other side of the country, in New Jersey and one man determined to stop the industry cold.

It's a big job but he's got a few things going for him. To start with he's a Kennedy.

"Did you ever picture yourself here.... family?"

PATRICK KENNEDY: [sitting on wharf holding son] "Oh just ah fake it till you make it, you know? It just happens and then you're like oh my God how did I get this lucky".

KNIGHT: As part of the Kennedy dynasty, Patrick, the son of Ted, the nephew of John F and Bobby Kennedy and the cousin of John Junior, knows all about political power. And he's made his own mark - he served in Congress for 16 years.

PATRICK KENNEDY: [Congress] "Families like mine all across this country know all too well what the damage of weapons can do, and you want to arm our people even more".

[tour of house] "This is my desk in Congress and in here a couple of special items".

KNIGHT: "This is the family history here. This is an artefact".

PATRICK KENNEDY: "This was President Kennedy's bomber jacket and he wore it as president and my late father had it and when my dad died, you know I was able to get it and obviously I love American history but it's also family history".

KNIGHT: "It's very much your history".

There's something else that's inspired Patrick Kennedy but it's not something he's proud of. It's the scarring and humiliating experience of his own profound addiction.

PATRICK KENNEDY: "That's the thing a lot of people who aren't addicts really don't understand, is that when you're in the middle of it, your ability to quote 'just say no' is totally hijacked by the illness that drives a compulsion to use. In other words, that compulsion is like automatic. It's like hardwired in your brain to just, I need more, I need more. I need to get relief. That's what addiction is".

KNIGHT: He admits he was an addict for most of the time he was in Congress. Pain killers, cocaine, opiates, alcohol - whatever he could get his hands on. It almost killed him.

In 2006 Patrick Kennedy was just out of detox but loaded up on prescription drugs and booze. He called it a night at a bar near Congress and got into his car. He crashed it into the barricades outside the Capitol building. Police drove him home. He was later charged, convicted and subjected to a year of weekly drug tests. It was a defining, life changing episode.

"On top of all that, you carry the Kennedy name. Now I wonder what it's like?"

PATRICK KENNEDY: "Yeah, yeah. That's enormously humiliating because I mean I would never have willingly chosen to humiliate myself and bring shame on my family. Not just once, twice, three, four, five times. I mean I have lost count of the amount of times that I said oh my God, look at what I've done to my family".

KNIGHT: Galvanised by shock and shame, the addict became anti-drugs advocate. Patrick Kennedy turned his life around and turned against the very things that almost destroyed him and that means "cannabis incorporated" is now in his line of fire.

PATRICK KENNEDY: "We need to make them enemy number one. No one has a visual yet as to who is behind Big Marijuana. So I want them to start coming out of the shadows. You know I welcome the fact that they're all starting to show up because I want the American people to really know what's motivating this whole industry and what it is, is big money - and it's greed.

(BILL CLINTON CLIP: "And I want to thank Patrick Kennedy for all he's done...")

KNIGHT: He's back on the campaign trail once again, only this time he's travelling the country and beyond, railing against the tide of legalisation.

And along the way he's making enemies.

DANA LARSEN: [protestor] "Using marijuana can be a very responsible choice, especially if you're choosing to use marijuana instead of alcohol or instead of tobacco".

KNIGHT: He's turning on the Kennedy charm trying to make a few friends where it really matters - the corridors of power in the US capital.

ADVISOR: 'What are we going to do with this federal strategy?"

PATRICK KENNEDY: "Well the real worry is now that we're going to have the banking system open to these industries in order to paddle this addictive drug".

DR KEVIN SABET: "There's a growing multi-million dollar effort on Capitol Hill in Washington to influence national marijuana legislation. They're able to, you know go in there, they.... like I said, they don't have the pony tail, they have their suit on and they are there to represent their clients and their clients want to make a lot of money off a lot of addicts".

[Speech] "What the research shows is that one out of six people - of kids - who are sixteen, who try marijuana will become addicted to it".

KNIGHT: Patrick Kennedy has enlisted an A list Washington insider to do his arm twisting here.

Kevin Sabet used to advise President Obama on drug policy.

DR KEVIN SABET: [speech] "The nature of marijuana is so different that when we test samples of marijuana today, the strength and purity has increased between five and seven times than even 20 or 30 years ago".

"Little by little this is about legitimising an industry. And so I think when people voted for this they weren't thinking about, well, will our banking industry now finance these cookies that are sending people to the hospitals. Is that what we want? This industry is not about hippies singing Kumbaya in a drum circle and smoking a few joints. It's about businessmen in suits making billions. They see bags of gold and money for them and they're going after it like any other industry would".

KNIGHT: Just like the big business that it aims to be, the cannabis lobbying effort is slick and well financed. Here in Washington, Cannabis Incorporated is working hard to convince the US Federal Government to get with the program and legalise marijuana as well. The states might be falling like dominoes but as long as it remains illegal under US Federal law, the retail roll out is tricky. So the industry is running a multi-million dollar hard-sell in the offices of house members and senators in the lobby land of K Street and in the nearby bars where the deals are often done. And that's where we catch up with Michael Correia, who heads up the National Cannabis Industry Association - the peak of the pot lobby.

MICHAEL CORREIA: "The Republican Party I think is going through a process where they're looking for a new demographic group, and I want to get politicians to understand that this is a winning political issue, especially with young voters".

KNIGHT: This former Republican staffer is pushing hard for law changes so corporate cannabis can get the same kind of breaks the alcohol industry gets, like access to conventional banking, finance, tax incentives and concessions.

MICHAEL CORREIA: "We had the economic downturn, we have a trillion dollar deficit and some of these state budgets are stressed. I think government, politicians and bureaucrats are looking for sources of revenue and this industry's actually the fastest growing industry in America. I think in the past five years you've seen more politicians open to discussing the economic issues and why there's a lot more traction with politicians".

PATRICK KENNEDY: "When you open up the spigots for the big money to use our banking system, to finance and use this commercial industry like any other, you are just going to put in place a mechanism that's going to be hard to break in terms of public advocacy. The public health will be a secondary thought because the primary thought will be how to make money off this industry".

JOHN DAVIS: "Look Patrick Kennedy had a severe drug problem. That doesn't make him a policy expert. No. You know it's done, over with. Everyone can see that. The policy is changing and you can't put the toothpaste back in the tube, so let's start having the conversations about how we're going to regulate and I'm happy to have that conversation with Patrick Kennedy but is it going to stay illegal? No.

KNIGHT: The policies may be changing, but the marijuana is changing too. It is more potent than ever and there are no plans to cap or control THC levels in retail dope. Opponents are worried that that is going to unleash a medical emergency.

DR KEVIN SABET: "They don't understand that today's marijuana can often times be upwards of 90% THC, you know extracted in a wax that's combusted and inhaled and that that often and can lead to emergency room admissions. I mean the idea for baby boomers that people are going to hospital for ingesting a marijuana cookie or one of these wax things on the end of a needle is totally foreign and yet that is the reality for a lot of kids today".

BRENDAN KENNEDY: "People have been consuming cannabis around the world for the last 5000 years and there's no known reports of cannabis causing an illness or causing death".

PROFESSOR LESLIE WALKER: "We're in a gold rush and this is a time when some people can become rich off a new product that's just coming on the market. I think that's the momentum".

KNIGHT: Back in Seattle, Professor Leslie Walker is bracing for a tidal wave of trouble. She heads up the division of Adolescent Medicine at the Seattle Children's Hospital.

PROFESSOR LESLIE WALKER: "Absolutely there's evidence that marijuana causes illness - in real life, in daily life, in research there's volumes of evidence that it causes illness. I mean one, I'm a doctor so I've seen it. I see in my clinic. I have a number of kids. The number one reason they come into my clinic for treatment is marijuana. And most of them have also depression or anxiety along with that".

KNIGHT: "And you believe that those mental illnesses have been caused or triggered by the marijuana use".

PROFESSOR LESLIE WALKER: "Caused, triggered or made worse".

KNIGHT: And Professor Walker can trace that back to the advent of medical marijuana and its availability to kids on prescription.

Soon they were turning up at her hospital with bigger problems. With retail marijuana she believes her team is about to get very busy.

PROFESSOR LESLIE WALKER: "Well I think what's happening is we're actually just recreating when tobacco began, you know over 50 years ago or more, the industry. And if you don't get addicted as an adolescent to a drug like marijuana, you're much less likely to become addicted as an adult. So if you have an industry, you want the young people to use, because that's your population. I mean the people that keep alcohol in business are the ones that drink a lot. You know, the people who have a drug problem, who need to drink - the people that are going to keep marijuana in business are the ones that are dependent on it and you need those people to begin as adolescents so we're going to see them want that to happen".

BRENDAN KENNEDY: "I think it's less addictive than tobacco. It's definitely less addictive than alcohol and less addictive than caffeine. I would feel comfortable being in the coffee business and I feel comfortable being in this business. I think that our number one objective is to end the harms caused by prohibition. We're in it for the long haul and our objective is to build mainstream global brands that can help facilitate the end of prohibition".

KNIGHT: Privateer is primed and ready to roll on an industrial scale.

A stone's throw over the border in Canada, they're operating a plant under a special agricultural licence that allows them to sell medical marijuana to their customers. It's effectively a prototype for the retail operation, cultivating, processing and packaging up retail products, under the brand name Tilray. "Til" as in tilling the soil, "ray" as in sunshine - very wholesome.

"Okay so here we've got Purple Kush, Island Sweet Skunk, OG Shark, Cannatonic and these.... so you've got four brands on there. Now you have more varieties in the factory but are these the four big sellers of premium brands?"

BRENDAN KENNEDY: "Four different strains. We have 40 strains in the building currently we're offering 14 strains for sale. So this is the package that we would use for a five gram shipment and this is Pink Kush, this is a hybrid and there's 23.4% THC".

KNIGHT: "Interesting that you're still using what is essentially I guess are the black market names, colloquial names that these things have been known by for a long, long time. Did you think of trying to rebrand them with something that doesn't have that connection?"

BRENDAN KENNEDY: "We did. You know what we wanted to do was come up with a very clean name like Tilray and we talked a lot about whether or not to keep the common names or come up with a branded name and ultimately we talked to patients and patients are really comfortable with the names that they're familiar with".

MICHALE BLUE: "You know for us it's about reaching the biggest audience with the most professional brand and a brand that provides a consistent, reliable product".

KNIGHT: Seattle and Washington State are about to become a part of America's biggest social experiment since it banned alcohol in the 1920s. Those who saw the end of alcohol prohibition coming made a fortune. Ironically one of those people was Patrick Kennedy's grandfather, Joseph Kennedy.

PATRICK KENNEDY: "People can always smoke marijuana, they can get it if they want it. The difference with commercialisation is now it's going to be actively promoted, much like alcohol is promoted. There are definitely going to be consumers and when they become consumers they're going to be customers, a good percentage of them, that are never going to leave you. Well if you're an industry I mean that's just like you've hit the jackpot".