A new book by biographer David Maraniss that delves into Barack Obama’s teenage years gives fresh insight into the president’s marijuana-smoking days as a high school student in the 1970s.

The book reveals how a teen Barack Obama and his friends formed The Choom Gang – slang for smoking marijuana – in which he invented inhaling techniques and rode a car called the Choomwagon.

In the book, Barack Obama: The Story, David Maraniss calls the future president “Barry” and reveals he “was known for starting a few pot-smoking trends”.

One was “total absorption” or “TA”, the rules of which stated that if you exhaled early, “you were assessed a penalty and your turn was skipped the next time the joint came around”.

Another idea was “Roof Hits” – rolling up car windows to stop smoke blowing out and going to waste.

“When the pot was gone, they tilted their heads back and sucked in the last bit of smoke from the ceiling,” David Maraniss writes in the book, excerpted on Google Books and due out June 19.

“Wasting good bud smoke was not tolerated,” an old school friend told the author.

And if that rule didn’t give enough of an insight into how much Barack Obama loved his marijuana, David Maraniss goes on to reveal he was known for his “interceptions” when a joint was being passed around.

“He often elbowed his way in, out of turn, shouted <<intercepted>>, and took an extra hit,” David Maraniss writes.

The anecdotes are from Barack Obama’s time studying at Punahou School in Honolulu, Hawaii and Occidental College in Los Angeles.

It is not the first time the spotlight has fallen on his teenage use of marijuana. In his 1995 autobiography, Dreams from My Father, Barack Obama made the admission himself.

Barack Obama wrote about some of his smoking haunts, including “a white classmate’s sparkling new van”, “in the dorm room of some brother” and “on the beach with a couple of Hawaiian kids”.

“Pot had helped, and booze; maybe a little blow when you could afford it,” Barack Obama adds in the memoir.

But David Maraniss is quick to point out that Barack Obama was surrounded with the drug in Hawaii – where a wide selection of varieties were on offer – and that “Barry” did not fit the stereotype of a teen pot smoker.

“In fact, most members of the Choom Gang were decent students and athletes who went on to successful and productive lawyers, writers and businessmen,” David Maraniss writes.

But they weren’t all destined for great futures. Ray, who dealt pot to the group and was known for his ability “to score quality bud”, was later killed by a “scorned gay lover” armed with a hammer.

Ray gets another mention in Barack Obama’s school yearbook as the teenager wrote his thanks to: “Tut [his grandmother], Gramps, Choom Gang, and Ray for all the good times.”

One of Barack Obama’s friends, Mark Bendix, had a Volkswagen microbus that they called “the Choomwagon”, the book continues, and they would use it to drive up Mount Tantalus in Honolulu.

Once parked, they “turned up their stereos playing Aerosmith, Blue Oyster Cult and Stevie Wonder, lit up some <<sweet-sticky Hawaiian buds>> and washed it down with <<green bottled beer>> (the Choom Gang preferred Heineken, Becks, and St. Pauli Girl)”.

The book also documents Barack Obama’s early democratic leanings, explaining that the group operated by consensus and any member could veto a suggestion.

“Whenever an idea was broached, someone could hold up his hand in the V sign (a backward peace sign of that era) and indicate that the motion was not approved.

“They later shortened the process so that you could just shout <<V>> to get the point across,” he wrote.

As well as in Dreams from My Father – in which he wrote he “got high [to] push questions of who I was out of my mind” – Barack Obama has been forthcoming about his use of marijuana.

When Bill Clinton’s claimed that he had tried marijuana but insisted he “didn’t inhale” in 2006, Barack Obama said: “That was the point, wasn’t it?”

Yet since coming into power in 2008, Barack Obama’s support for the substance has waned, enforcing strict penalties for drug use – that would have prevented his presidency if he himself had been caught.