According to federal drug regulations, Michael Jackson's personal physician couldn’t legally prescribe even a powerful cough medicine for the King of Pop in California, and he couldn’t go to the pharmacy to get drugs for him, either.

Federal authorities told FOXNews.com that Dr. Conrad Murray is not licensed to administer certain levels of controlled medications in the state, and that if he gave Demerol or Oxycontin to Jackson, as has been reported, it would have been illegal.

To possess the drugs in California, Murray would have had to bring them with him from Nevada or Texas, which is illegal, or administer drugs that other doctors had provided locally or that Jackson had ordered online from abroad, which is also illegal.

Murray's lawyers insist that the doctor didn’t give Demerol or OxyContin to Jackson. Murray's attorney, Ed Chernoff, released a statement Monday declaring “Dr. Murray didn’t prescribe or administer anything that should have killed Michael Jackson.”

Federal law requires doctors to register with the Drug Enforcement Agency in the jurisdiction in which they administer, dispense or prescribe controlled substances ranging in potency from extra-strength cough syrup to potent painkillers. Murray is licensed to practice medicine in three states, and he is required to register with the DEA in all three if he wants to be able to provide equal drug treatment to all his patients.

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“Dr. Murray has DEA registration numbers in Nevada and Texas, but he does not have one in California,” a federal law enforcement official told FOXNews.com. “You absolutely have to have a registration number to prescribe controlled substances, and there was nothing in California.”

This means that despite being medically licensed in the state of California — and despite being hired as personal physician to Jackson, who lived in that state — Murray was and is not allowed to administer, dispense or prescribe drugs classified as Schedule II, III, IV and V controlled substances.

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Potency decreases as schedule numbers increase: Schedule V drugs include codeines like Robitussin A-C and Pediacof; Schedule IV: Valium, Xanax, Ambien, Sonata, Lunesta; Schedule III: Anabolic steroids, Vicodin; Schedule II: Demerol, OxyContin, Percocet, Ritalin. Schedule I drugs, like heroin, PCP or Peyote, have no medicinal purposes.

The intravenous anesthetic Propofol, whose brand name is Diprivan, is not classified by the DEA as a scheduled drug, due to the rarity of its abuse and the dangerous level of potency and monitoring involved in administering the drug, which normally occurs only in a hospital setting.

Miranda Sevcik, a spokeswoman for Murray's legal team, said she did not have information about the doctor's DEA registration status in California.

"We don't have that information," she said. "If it's relevant to the investigation, I'm sure it'll be looked into. If it's not, it won't be."

Last Monday, investigators with the Los Angeles County Coroner’s Office removed two bags filled with prescription medications from Jackson’s Holmby Hills home. Among the drugs recovered were bottles of Diprivan, at least some of which were found without labels indicating where they came from, law enforcement sources told FOXNews.com.

"We're not answering to questions about Diprivan nor are we answering to any substance, food or drink that could be found in his system as well," Sevcik said. "We just don't know at this piont. That is why we're waiting on the official report."

Murray's attorney, Chernoff, said any drugs the doctor gave Jackson “would have been prescribed in response to a specific complaint.”

Jackson complained to Murray that he was having trouble sleeping, the doctor's attorneys said, but sleeping pills like Ambien or Sonata fall into the Schedule IV category, and Murray would not have been legally allowed to prescribe them.

Depending on the results of Jackson’s autopsy report — the full toxicology results won’t be back for another few weeks — criminal cases could be pursued if violations of federal drug laws are found to have caused his death.

Jose Martinez, a spokesman for the DEA in Los Angeles, said his office was referring all media inquires to the LAPD, offering only this statement: "We routinely offer assistance to any agency regarding the Federal Controlled Substance act, however at this time we have nothing further to comment about the death of Michael Jackson"

The LAPD did not respond to requests for comment. It has called Murray a cooperating witness.

As investigators work to track down the source of numerous prescriptions found in Jackson’s home, they are also checking up on the cadre of doctors who became part of the King of Pop’s final inner circle. Murray was one of its newest members; he met Jackson just three years ago.

In late 2006, Michael Jackson returned to the United States after a year of self-imposed exile following his acquittal on child molestation charges. After months in Bahrain, and then in Ireland, Jackson and his three children arrived in Las Vegas amid swirling rumors of a comeback concert series there.

When Jackson’s daughter, Paris, then 7, became ill, he asked his security detail if anyone knew of a concierge doctor who could come by the house to check on her. One of his bodyguards said he knew a guy: Dr. Conrad Murray.

Murray, a cardiologist who runs a practice in Las Vegas and another in Houston, makes house calls to high-profile clients in Sin City — and in Washington and New York.

Friends and former patients say his Zen-like manner, holistic approach to healing and Chopra-esque spirituality likely contributed to the forging of his friendship with Jackson.

It was that friendship, not Murray’s specialty in cardiology, that led Jackson to chose Murray to join him on tour, Murray's attorneys say. In May, Murray signed on in an official capacity to be Jackson's personal physician — to the tune of $150,000 per month — for the duration of his 50-concert series in London. Murray says concert promoter AEG LIVE currently owes him $300,000, according to his attorneys.)

The money was one of the main reasons Murray decided to go on tour with Jackson, says Rev. Floyd Williams, 80, who is Murray's friend and patient. Murray had developed a booming concierge business — he was jetting off to see patients in New York and Washington while building his practice in Las Vegas. Three years ago, Murray joined the Freemasonry, the international fraternal society that dates back to the early 17th century. His friends say this new network galvanized his growing side business.

But despite his success, Murray's clinic in a lower-middle-class neighborhood in Houston had been hemorrhaging money. His patients couldn’t pay, and Murray couldn’t cover the costs. But he wanted to keep the clinic open, his friend said, so he took out a series of loans.

Williams said that Murray asked him whether he should leave his patients to go on tour with Jackson. He said he encouraged Murray to go, to make loads of money, and then to come back and continue to operate his growing practice —and to keep the clinic open — without the crippling debt.

In May, Murray said yes to Jackson, and in the last few months he made several trips to Los Angeles to work out the details of the contract and to meet with the star. One of Murray's patients, Donna DiGiacomo, 51, said she had heard that Murray had asked a colleague — a hospital doctor — to join Jackson’s medical team, but that doctor said he could not leave his family and business for such a long period of time.

Murray stayed at his own place in Los Angeles on most nights. But when asked, and only on occasion, he spent the night at Jackson’s rented Holmby Hills home, one of the doctor’s attorneys, Matt Alford, told FOXNews.com in an earlier interview.

On June 24, Jackson finished up a rehearsal at the Staples Center and asked Murray to stay the night. The next day around noon, Murray went to check on Jackson and found him lying on his bed unconscious, but with a weak pulse, the doctor's attorneys say.

Murray performed CPR for about 30 minutes and tried to call 911, but could not call out on the landlines, which had been turned off for security reasons. He could not use his cell phone because, his attorneys have said, he did not know the exact address of the house. After performing CPR on Jackson, who lay on his bed, for approximately 30 minutes, and after yelling out for someone else in the home, he left the pop star to try to find someone who could call 911. He found a chef in another part of the house. The chef then found a bodyguard, Alberto Alvarez, and while Murray rushed back to Jackson’s room and continued CPR, Alvarez called 911.

The time was 12:21 p.m.

Paramedics arrived three minutes later and worked on Jackson at his home for approximately 40 minutes before he was transported to UCLA Medical Center. Jackson continued to have a pulse while he was in the ambulance, according to Murray.

At 2:26 p.m., Jackson was pronounced dead. Murray says he broke the news of Jackson’s death to his three children, Prince Michael, 12, Paris, 11, and Blanket, 7, outside the emergency room.