March 24, 2012 -- Marijuana was the best medicine for 3-year-old Cash Hyde of Missoula, Mont. At least that's what his parents, Mike and Kalli Hyde, believe.

The couple said they defied doctor's orders -- and Montana law -- to get their hands on the medicinal treatment their son needed after he was diagnosed with recurring brain tumors at 22 months old.

"I've had law enforcement threatening to kick my door down, but I would have done anything to keep Cashy alive," Mike Hyde, who said he has long been a proponent of the drug, told ABCNews.com.

Hyde said police sought out the Hydes after they publicly spoke about how Cash's health benefited from cannabis oil. Mike has not been arrested, although he said police have threatened to.

But Missoula Police Sgt. Travis Welsh said he was unfamiliar with the Hydes' case, and he assured that this is not a black and white situation.

"This is not a situation that we routinely run into," Welsh told ABCNews.com. "There are a lot of different variables to consider in this situation. I can't imagine we'd go out right away to arrest this dad for a drug offense. But there are other factors, including whether it's appropriate for somebody to act independently of doctor's orders and whether they are acting in the best interest in the child."

"Obviously, this man's intentions are for his child," Welsh said.

The Hydes and doctors decided to wean the toddler off a cocktail of drugs that included, methadone, ketamine and morphine. Their son went through 30 rounds of radiation without one nausea or pain medication besides medical marijuana, according to his father.

Mike Hyde said doctors were unaware he was giving his son marijuana.

Doctors told the Hydes that Cash only had a 30 percent chance of surviving five years, and, at best, radiation could stop the tumor from spreading. But the toddler, whose second tumor was diagnosed in October, has not seen any recurrence. His parents chalk that up to the cannabis oil they administered to him twice a day since the second tumor diagnosis.

Mike Hyde said he traveled throughout Montana and California to obtain the cannabis oil for Cash. To figure out the proper dose to give to his son, he researched the suggested numbers for adults, "then gave the proportional dose for Cash's weight."

"Before he ever received any oil, I'd give myself 10 times the amount I was going to give him to be sure of the effects," Hyde said. "I came to the conclusion that this drug was safer than any other drug for him."

"No one can read this story without being happy for the child and his family; however, one cannot assume the cannabis oil is responsible for the remission or even the relief of pain," said Dr. Donna Seger, associate professor of clinical medicine at Vanderbilt University School of Medicine. "He may be one of the fortunate few in which remission would have occurred no matter what treatment had been administered."

More than 14,000 Montana residents hold a license to use medical marijuana, according to the state's department of public health and human services. Under Montana law, a person under 18 can become a medical marijuana patient, but their parent or legal guardian must agree to act as the minor-patient's primary caregiver and control their use.

The drug has been approved by the Food and Drug Administration to relieve symptoms of nausea and vomiting, and to help increase appetite in people with cancer and AIDS, according to the American Cancer Society. The most potent ingredient of medical marijuana is THC. The product comes in the form of an inhaler, pills and oil, which Cash was given, and it can also be smoked.

There are no other drugs that work as well as cannabis for treating the nausea and anorexia associated with cancer and its treatments, said Seger.

Even with the pain-reducing qualities of medical marijuana, Dr. Allison Dering-Anderson, clinical assistant professor in the College of Pharmacy at the University of Nebraska Medical Center, said most states' medical marijuana laws likely would not cover a child as young as Cash.

And while Dering-Anderson said she is happy that the boy is recovering, she does not condone breaking the law in this way.

"It's not acceptable to break the law," said Dering-Anderson. "I'm sorry for this child and for this family and for all they've gone through, but….our licenses depend upon upholding the law."

Dering-Anderson said she has deep concerns about children taking medication that is not specified by a doctor and without clear oversight of their care.

"This child wasn't involved in a controlled study," she continued. "It's a good thing that this product didn't harm him. Would this have been news if the parents had used cobra venom or poison sumac? I doubt it."

Nevertheless, his parents are happy he is alive and well, and chalk it up to the marijuana as a major reason why Cash is "playing with Play-Doh," and not confined in a hospital bed, without energy to do any of the things children normally do.

"Cancer is a terrible monster," said Mike Hyde. "I was going to do anything to help my child."