The Canadian military will severely restrict — and in some cases prohibit — the use of recreational marijuana once it becomes legal this fall.

National Defence released its formal policy on Friday along with the accompanying regulations, which impose limits on cannabis use that are more wide-ranging than those governing alcohol.

The head of personnel, Lt.-Gen. Chuck Lamarre, said the military has been focused on putting "the right prohibitions" in place and believes the new rules strike an appropriate balance that will respect the law while allowing the Canadian Armed Forces to do its job.

The marijuana policy will not be more difficult to enforce than the current policy on alcohol, he said.

"We've made the policy document very explicit as to when it can be used and when it cannot be used, and who is prohibited from using, and we go to a large extent to protect our operational capability."

The regulations state members of the military are barred from consuming cannabis within eight hours of being on duty, and they aren't allowed to smoke or ingest it during the work day.

The policy covers both uniformed and civilian members.

For those handling weapons and ammunition, conducting firefighting or medical response, the consumption restriction will be extended to 24 hours before duty.

Those in "safety-sensitive" positions will have to abstain for 28 days before being allowed to do their jobs.

There is a outright prohibition on use while members are serving on operations at home and abroad, and during training periods.

Marijuana will not be allowed on military aircraft or ships.

According to the new military directive, individual branch commanders — including the heads of the army, navy, air force and special forces — will have the authority to enact further restrictions as they see fit.

Recreational marijuana will become legal on Oct. 17. The military has been working for over a year to decide how it will deal with what promises to be an enormous institutional change.

The military has signalled for months that the rules surrounding cannabis would tighten, but those rules would be founded on "science." Officials noted the compounds in cannabis can be detected in the body for "seven or eight days, and we're putting even more restrictions on that to make sure there's no chance somebody would be affected by it."

Tetrahydrocannabinol (THC) — one of those compounds and the primary psychoactive constituent of cannabis — can linger in the bloodstream for up to 72 hours and impair a user for up to three hours, according to science journals.

The military has long had a zero-tolerance policy on drug use. It also has a long-established drug testing policy for "safety-sensitive" positions.

The country's top military commander, Gen. Jonathan Vance, said in a general order that testing will continue to be conducted on individuals "where appropriate" in so-called 'restricted' occupations.

Those restricted categories include pilots, aircrew, search and rescue technicians, submariners, divers and flight surgeons, among others.

For those not serving in such high-pressure occupations, the military rules will be similar to those governing the consumption of alcohol: if someone shows up at work and their supervisor suspects they are stoned, they can be suspended from duty and referred to medical technicians.

The new policy gives the military the authority to demand urine, blood and saliva samples in the event of an accident where impairment is suspected.

A military expert said there could be an administrative and legal minefield ahead for the military.

"It appears to be a reasonable response by the Canadian Forces to the legalisation of marijuana, on its face," said Rory Fowler, a former lieutenant-colonel and military lawyer, now in private practice.

"My biggest concern is how it's going to be implemented and how it's going to be treated by the chain of command. Because the chain of command has this instinctive response to cannabis use that, in some ways, strikes me as unreasonable."

Throughout the development of the policy, there has been intense internal debate among the various branches of the military, with some arguing for a total prohibition in some occupations.

The military's former judge advocate general, Blaise Cathcart, argued — both behind closed doors and in public — that banning marijuana in the military, once it's legal, would be an uphill battle.

A few years ago, senior leaders within the military argued for an expansion of the number of occupations subject to mandatory testing. The proposal was rejected.

Fowler said the law of the land may change, but attitudes within the military likely won't.

"If they overreact and start hammering people — overreacting because how dare you smoke marijuana — then they're going to use administrative measures much more readily than disciplinary measures," he said.

Those administrative measures "don't undergo the same legal scrutiny," he added.

Lamarre said the military expects and is prepared for legal challenges of the marijuana policy, and plans to review the policy on an annual basis as the science around marijuana use evolves.

Since 2007 the military has conducted random blind drug sampling tests and the results have shown consistently that marijuana has been the illegal drug of choice in the military — more popular than cocaine and other hard drugs.

"We believe our members are very keen on what they're doing in the Canadian Armed Forces and they have the right ethics and morals to make sure they are available at all times and that they are not impaired by this, or any other substance," Lamarre said.