When it comes to celebrity cannabis activists, Woody Harrelson - who turns 55 today - is one of the longest running and most outspoken opponents of marijuana prohibition. The actor and avid cannabis connoisseur has lent his star power to fight for legalization and to celebrate cannabis culture.

Here are his best marijuana moments to date.

1. Woody and Willie's Marijuana Restaurant

The Hawaiian dispensary isn't the first time Harrelson has considered going into the cannabis industry. While promoting the animated feature Free Birds (2013), Harrelson toyed with the idea of teaming up with Willie Nelson to open a marijuana restaurant in Denver.

Sadly, the venue - tentatively named "The Mile High Club" - never came to fruition. Nor did Owen Wilson's idea of a rival eatery called "The Mile Higher Club," which he joked about opening with Snoop Dogg:

2. Life, Liberty and the Pursuit of Cannabis

While he doesn't mind joking about marijuana, Harrelson also treats it as a serious issue of personal freedom and American values. In a 2005 interview with 420 Magazine, he said,

"I do smoke, but I don't go through all this trouble just because I want to make my drug of choice legal. It's about personal freedom. We should have the right in this country to do what we want, if we don't hurt anybody. Seventy-two million people in this country have smoked pot. Eighteen to 20 million in the last year. These people should not be treated as criminals."

3. Defending Marijuana's 'Distant Cousin'

Along with speaking out in favor of marijuana legalization, Harrelson also opposes the federal prohibition of hemp, which is like marijuana's straight-laced cousin: the two plants are related, but hemp does not make you high.

In 2010, Harrelson teamed up with Ralph Nader, Willie Nelson and others on the documentary "Hempsters: Plant the Seed", which exposes the corruption behind the criminalization of hemp. (Spoiler alert: petrochemical companies don't want the American economy switching to industrial hemp even though it's a versatile, sustainable and ecologically friendly alternative.)

Check out this clip from the documentary, where Harrelson talks about the "American plant" and taking power away from petrochemical corporations and putting it back in the hands of the people:

http://www.youtube.com/watch?v=fHhzWzuXLuM

4. American History on Cannabis

"Hempsters" isn't Harrelson's first foray into documentary making. Back in 1999, he narrated the iconoclastic film "Grass," which took on the anti-cannabis establishment by highlighting the hypocrisy and absurdity of cannabis prohibition in America. The film premiered at the Toronto went on to become a cult hit and won Canada's Genie Award in 2001.

Check out the NSFW trailer:

5. The Original Ghostbusters Reboot

Long before Kristen Wiig, Melissa McCarthy and Kate McKinnon signed up for the 2016 Ghostbusters reboot, Woody Harrelson (as Tallahassee) and Bill Murray (as "himself") smoked a bowl and reenacted a classic scene in Zombieland (2009), where Murray plays Ray, Harrelson plays Venkman and Emma Stone plays Janine.

h/t The Globe and Mail, Leafly, Gizmodo, NY Daily News, Esquire

Banner image: Woody Harrelson attends the 2015 London premiere of The Hunger Games: Mockingjay - Part 2. (Twocoms / Shutterstock.com)