Imagine losing your smartphone or leaving your laptop behind on a train or bus. How much could someone learn about you — your interests, your lifestyle, your habits — based on what they could access on the device?

What conclusions could someone make when the photos you've taken, the apps you've installed and the websites you've visited are laid bare?

According to the Supreme Court of Canada: quite a few.

Unlike a briefcase or a filing cabinet, judges have found, a smartphone can contain "immense amounts of information" that touch a person's "biographical core."

They've acknowledged that laptops create detailed logs and trails of data that can be used to retrace a person's steps in ways that physical documents can't.

And lawyers have successfully argued that smartphones and laptops, far from being static stores of information, are in fact portals to the near-limitless volumes of data stored in the cloud — from social media profiles to email accounts and file-sharing apps.

The question is simply, do you have a reasonable expectation of privacy in your device at the border? — Rob Currie , Dalhousie University law professor

It was in this context that a Manitoba provincial court judge last year made a significant ruling: just as Section 8 of the Charter of Rights and Freedoms protects Canadians from unreasonable search and seizure, that right should also apply at the border when an officer asks to search your smartphone or laptop.

Privacy at the border?

The details of the Manitoba case have become increasingly familiar to lawyers across the country. During a routine border crossing in May 2014, officers of the Canada Border Services Agency asked to search Brandon Vaillancourt's car.

Inside, they found an unlocked iPhone running a GPS navigation app and decided to search it. They wanted to see whether Vaillancourt's messages and photos supported his description of his travels in the U.S. In the process they found what they believed to be child pornography, and Vaillancourt was subsequently charged.

Vaillancourt was ultimately convicted — but in the process, the judge called into question the federal government's long-held position that the Customs Act gives it the broad power to search personal electronic devices without a warrant or limitations, under its definition of importable goods.

Naturally, lawyers for the federal government were not happy, and in May announced their intent to intervene in Vaillancourt's appeal. They plan to argue the law is fine as is.

But it may not be the last time they feel compelled to do so. Across Canada, an increasing number of lawyers are arguing more or less the same thing: that warrantless smartphone searches at the border are unconstitutional, and the practice should be stopped or at least limited.

"The question is simply, do you have a reasonable expectation of privacy in your device at the border?" said Rob Currie, director of the Law and Technology Institute at the Schulich School of Law at Dalhousie University.

The government has consistently argued no.

'Travellers do not expect the same degree of personal privacy at national borders as they do in other situations,' Alberta Crown prosecutor Carolyn Ayre argues. (Jonathan Hayward/The Canadian Press)

'A big gap' in Canadian law

CBC News has learned of four cases which lawyers are arguing their clients' electronic devices were unlawfully searched under the Customs Act. Three follow a common theme — the discovery of child sexual abuse material on electronic devices belonging to the defendants — and one is a drug trafficking case.

"The authority under the Customs Act is pretty large and vague," said Paul Gracia, a defence lawyer involved in one such case. "And that's where the courts have interpreted goods as including cellphones and the electronic data on them. So that's going to have to change."

All of the known cases — including Gracia's — have been heard in lower courts, so any decision would have to advance to the Supreme Court to have widespread effect. But legal experts have said it's only a matter of time before that happens.

"We don't have a constitutional ruling on the legality of warrantless searches," said Brenda McPhail, director of the Canadian Civil Liberties Association's Privacy, Technology and Surveillance Project, who has extensively studied border search policies. "That is a big gap in Canadian jurisprudence."

Are smartphones and laptops 'goods'?

Each of these cases focuses on Section 99(1)(a) of the Customs Act, which gives border officers the power to, "at any time up to the time of release, examine any goods that have been imported and open or cause to be opened any package or container of imported goods and take samples of imported goods in reasonable amounts."

The government considers smartphones, laptops, and other electronic devices to fall under this definition of goods — no different from papers in a briefcase.

Defence lawyers have argued against this, pointing to Supreme Court decisions such as R. vs. Vu that have found electronic devices are very different from other, more traditional storage receptacles.

"It is difficult to imagine a more intrusive invasion of privacy than the search of a personal or home computer" given the "immense" amounts of personal information they can store, wrote Justice Thomas Cromwell for R. vs. Vu's deciding majority. In that case, electronic devices belonging to a man arrested on drug-related charges were improperly searched under a warrant to search the man's home.

The Canadian Civil Liberties Association calls Canada's customs legislation 'briefcase law' because it predates smartphones and laptops. (Lucas Jackson/Reuters)

The government, however, disagrees.

"There is no reason to think that electronic goods require a different approach," wrote Alberta Crown prosecutor Carolyn Ayre in a submission during one of four cases reviewed by CBC News. She also argued that "travellers do not expect the same degree of personal privacy at national borders as they do in other situations."

Briefcase law

In Manitoba, the Vaillancourt case is the first in which a judge has ruled on the constitutionality of searches conducted under the Customs Act.

In his decision last year, Judge Donovan Dvorak ruled that if border officers are to search phones, they have to abide by the limits defined in the 2014 Supreme Court case R. vs. Fearon, which dealt with cellphone searches incidental to arrest. It was decided that for a search to be lawful in such scenarios, there would have to be a relevant law enforcement purpose for the search, the search could not be indiscriminate, and officers would be required to take detailed notes on what was searched and how.

'A pre-smartphone statute'

But it's not yet clear if Judge Dvorak's ruling will stick. Federal government lawyers argued in May they should have been notified before such questions were raised to give them the chance to respond. The Crown has since been granted the chance to submit arguments that the law is reasonable as is.

Even if that ruling does ultimately stick, CCLA director McPhail argues that it doesn't go far enough. While the decision imposes limits on when smartphones can be searched at the border, McPhail believes those limits could be stronger — and that electronic devices should not be considered goods.

"The Customs Act is a pre-smartphone statute," reads a submission by the CCLA, which intervened in Ontario in R. vs. Sikailey.

"It contains no provisions applying specifically to phones or digital devices. Nowhere does it even use the words 'phone' or 'digital device.' It does not even refer to digital storage. It is briefcase law."