The Canadian military will not be in a position to impose an outright ban on the use of recreational marijuana, but its restrictions will be more wide-ranging than its policy governing alcohol, says a senior commander.

A draft policy is waiting in the wings for the Liberal government to pass C-45, the cannabis legalization bill, which was sent back from the Senate to the House of Commons with a long list of amendments last week.

The new policy "allows us to respect the law," Lt.-Gen. Chuck Lamarre, chief of military personnel, said in a recent interview.

"But at the same time, I think Canadians are expecting our operational readiness and our ability to do our business must never be compromised."

The directive will cover everyone in uniform but also offer guidance for the 30,000 civilian employees of National Defence who support military operations, directly and indirectly.

If the law says it's no longer criminal to have it in your possession, it's not a criminal act. - Lt.-Gen. Chuck Lamarre

The use of alcohol in the Canadian military has been subjected to various restrictions, and even outright bans, during some overseas operations.

What Lamarre and his team appear to be proposing, after months of legal and medical study, is essentially an expansion of that regime to reflect the unique nature of cannabis.

"There's no total ban at this point," he said. "We can't do that. If the law says it's no longer criminal to have it in your possession, it's not a criminal act. You just can't ban it outright."

There are some within the military who have been arguing for an outright ban for certain occupations, notably pilots.

Lamarre would not discuss the particulars, but acknowledged the air force has "specific concerns" and the new commander has been asked to identify where the new rules need to be tougher.

In addition, each of the branch commanders — for the army, navy, air force and special forces — has been asked to designate certain jobs which will be subject to restrictions.

Essentially, they're expected to say: "I need to restrict the following occupations for these periods of time, under these circumstances," said Lamarre, who emphasized the senior leadership will "be very specific."

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

The justification for the tighter rules is founded on "science," said Lamarre, noting that 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 can impair a user for up to three hours, according to science journals.

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

Lamarre said he doesn't envision much in the way of changes to the current testing regime.

Marijuana is the illegal drug of choice in the military

As recently as five years ago, National Defence faced an intense internal lobbying campaign from senior commanders who wanted to see the list of occupations subject to drug screening drastically expanded.

Since 2007, the department also has conducted random blind drug tests involving thousands of members across the country.

Reports on those tests have shown consistently that, over the years, marijuana has been the illegal drug of choice in the military — more popular than cocaine and other hard drugs.

A 2013 analysis of the army, released to The Canadian Press under access to information legislation, found young, non-commissioned members were more prone to drug use.

Out of 279 urine samples collected at bases across the country, 6.6 per cent tested positive for one drug, with cannabis detected in 5.3 per cent of all samples.

Lamarre said he doesn't believe there will be a spike in marijuana usage among members of the Armed Forces when it becomes legal. Most people who join the military, he said, join it to do challenging things, such as flying planes and helicopters, and anything that keeps them away from that work tends to be shunned.

"I don't anticipate a whole whack of sparking up," Lamarre said with a chuckle.