Transcript for 'This Week' Game Changer: Marijuana Legalization
My game changer for 2014 is asian Pugh. She won the MCC My game changer for 2014 is ai-gen poo. She won the Mccarthy genius award by getting rights for domestic workers and nannies which is the first time that's happened in the history of the country. My game changer is Taylor swift for two reasons. She's teaching the younger generation that you can be a lady, and she's teaching song writers and musicians that they can control their future. Back now with a story of a remarkable year for marijuana. After the story cleared the way for legal pot industry in the several states, we take a look at how it's working and what's next for an experiment stirring up all kinds of debate. You want to get high, man? Is that a joint, man? Reporter: Remember cheap and Chong, those hapless stoners from the era of up in smoke? 40 years later, they finally arrived. Tommy Chong on ABC's "Dancing with the stars," talk about a game changer. An icon of the counter-culture, dancing the cha cha on one of America's most popular mainstream shows. Doesn't he look like the most interesting man in the world? Most interesting stoner. Reporter: America's war on drugs is not over yet. Over the past few years, we've seen state after state surrender on the issue of cannabis. Have we reached the tipping point? I think we have reached the tipping point. The polls consistently show that half or more of the people who oppose the legalization of marijuana think it's inevitable. Reporter: Medical marijuana is now legal in 23 states, nearly half the country. Four states are experimenting with full legalization. And now for the first time ever, congress has rolled back the war on drugs through a spending bill which, while it's squashed d.c.'s hopes for a full legalization, enacted a hands-off approach for states that are relaxing their pot policies. The times, they are a-changing. Public enemy number one is drug abuse. Reporter: From Nixon on down to Reagan. Drugs are menacing our society. Reporter: And bush -- Our 1990 drug budget totals almost $8 billion. Reporter: The war on drugs has been costly. We've got a problem in this country. Too many people use drugs. Reporter: By the time Obama took office, the drug enforcement budget had doubled again, more than $15 billion a year. So the idea that marijuana has now been legal in Colorado for a full year with no major disasters is a big development. I didn't support the initiative, but you can't argue with the will of the voters. Reporter: Colorado officials have been true to their word, embracing the challenge of implementing a policy many of them disagreed with. Let's be smart about how we handle it, let's legalize it, tax it, and make sure that people are held responsible for the responsible use of it. Reporter: One year in, violent crime rates are down. Teen marijuana rates have actually dropped. Highway fatalities are at record lows. And Colorado has the fastest growing economy in the country. What have the tax revenues been like in Colorado? It's been more than has been expected. It's going to add up clearly to hundreds of millions of dollars very quickly per year. Reporter: To be sure, not everyone is a believer. Today's marijuana is not your woodstock weed of the '60s. It's five to six times greater in strength P and potentsy. When you have is a disconnect between the parents that might have smoked it a couple times in college and were fine and today's marijuana which is much stronger than it used to be. Reporter: Stronger and health officials worry easier for young people to get their hands on. Any time you legalize a drug it increases access. Reporter: Posing a bigger threat to a teenager's developing brain. Reporter: Brain development occurs from age ten well into your 20s. The latest study shows that regular use when you're an adolescent is associated with a six to eight-point reduction in iq. Reporter: There is a chance that the courts or the candidates will roll it all back, but that seems less likely now. From Chris Christie in new Hampshire -- If you were president, how would you treat states that legalize marijuana? Probably not well. Reporter: To Hillary Clinton on CNN, the debate seems to have shifted to just say no to a qualified maybe. States are the laboratories of democracy. We have at least two states that are experimenting with that right now. I want to wait and see what the evidence is. Reporter: Contrast that with bill Clinton and his famous answer to the pot question a generation ago. When I was in England I experimented with marijuana a time or two and I didn't like it. I didn't inhale and never tried it again. Reporter: The last two presidents flatly admitted they tried it long ago. President Obama telling "The new Yorker" this year he sees marijuana as a vice, a bad habit like cigarettes and alcohol. Prohibition for marijuana won't end with a 21st amendment. But make no mistake, it is already ending. In 2004 tommy Chong was in federal prison, cell mates with "The wolf of Wall Street" for selling bongs. A decade later, he almost made the finals of "Dancing with the stars." I was going to turn the mirror ball into a mirror bong. Reporter: Pop culture, embrace it. The counter-culture. For "This week," David Wright, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.