Willie Nelson has long been a proponent of legalizing marijuana. The singer, who has faced several arrests for drug possession, explains why he feels so passionate about the cause.

"One word: Money," he tells CelebStoner.com. "There's a lot of money in selling marijuana. If you can do it legally, that's good. Why should all the criminals make the money? This is what people are thinking. If it's happening, if it's going to be legal, let's tax it and regulate it, like we do with everything else and make some money off this. I think that's one reason why people are talking this a little more seriously."

Still, the 81-year-old says he is cautiously optimistic that all 50 states will soon make the narcotic legal.

"I think it has a lot to do with Colorado and Washington, all the states that have legalized it," he notes. "That's a big deal. I probably was one of the most surprised. I didn't think it would happen in my lifetime, but here it is. The future looks good."

In fact, the Texan admits that the Governor's office in Colorado already reached out to him about doing a PSA to advocate for the cause.

"Yeah, we've talked about doing a couple of things," Nelson reveals. "I don't know, I may or may not do it. I haven't decided yet."

One thing the country music hitmaker says everyone who feels passionate about the cause can do is hit the polls.

"Find out who in their area believes the way they do and vote for them," he urges. "Get out and go vote. If it's the day to go vote, make sure you go vote before you burn one down. Don't get high and forget to vote."

Nelson included his thoughts on marijuana in the song, 'Roll Me Up and Smoke Me When I Die' from his 2012 album, 'Heroes.' Download the single here.