Demanding a breath sample from a motorist is no different than asking for their licence and registration, Canada's justice minister argued Thursday as the federal Liberal government defended its proposed new crackdown on impaired driving.

Jody Wilson-Raybould tabled a so-called "charter statement" in the House of Commons explaining why the government believes the new measures are permissible under the Charter of Rights and Freedoms.

"The Supreme Court of Canada has recognized as reasonable the authority, under provincial law and common law, of police officers to stop vehicles at random to ensure that drivers are licensed and insured, that the vehicle is mechanically fit and to check for sobriety," Wilson-Raybould's statement says.

"The information revealed from a breath sample is, like the production of a driver's licence, simply information about whether a driver is complying with one of the conditions imposed in the highly regulated contexts of driving."

Bill C-46, which includes new powers for police and harsher penalties for driving under the influence of alcohol or drugs, was introduced in the Commons last month alongside the government's long-awaited plan to legalize marijuana for recreational use.

The new mandatory alcohol screening measures would mean police could demand a breath sample from any driver they lawfully stop -- even if they had no suspicion the person had been drinking before being pulled over.

The roadside test itself could not lead to a charge, but it would allow the police to continue investigating and to subject the driver to further tests.

The bill would also allow police to demand a saliva sample from a driver if they reasonably suspect the person has drugs in their body, such as by noticing unusually red eyes, abnormal speech patterns or the telltale scent of marijuana.

The proposed legislation has raised eyebrows among some criminal lawyers, who believe it will be challenged in court.

The statement outlines why the Liberal government considers the new powers to be consistent with charter guarantees about search and seizure, as well as life, liberty and security of the person.

It points out, for example, that while the bill would eliminate the need for reasonable suspicion of drinking and driving, it would still only apply if the driver was lawfully stopped in the first place.

The statement does come with a major caveat: "A statement is not a legal opinion on the constitutionality of a bill."

The statement also says Bill C-46 would help the Liberal government achieve its "compelling objective" of cutting down on drinking and driving. Currently, it can be difficult for officers to identify a driver who should be administered a breath test.

"It would reduce the impact of this kind of human error," it says. "It would also increase the deterrent effect of roadside stops by eliminating the perception that motorists could avoid having to give a sample by hiding their impairment."

Research done in other countries that have taken a similar approach, including Australia, New Zealand and Ireland, has shown a substantial reduction in alcohol-related accidents and even deaths, the government argues.

Anthony Moustacalis, president of the Criminal Lawyers' Association, said he is concerned the new law could lead to a higher number of random stops of visible minorities.

"I think the one area of constitutional attack would be that, given the developing statistics on subconscious racism by the police, or unconscious racism, and the increased empirical data on misuse of random stops by police for visible and other minorities."

Robert Solomon, national director of legal policy for MADD Canada, said people already have to go through mandatory screening in order to do all sorts of things.

"Mandatory alcohol screening serves exactly the same protective purpose as airport, border and courtroom searches, but is far more effective and addresses a far greater risk," said Solomon, who is also a law professor at Western University in London, Ont.