What follows is legal information for the education of the public, not legal advice with regard to a particular situation. If you need legal advice, obtain it.@CheckStopEdm is a twitter handle that reports the location, and advice for avoiding, check stops in the Edmonton area. A Check Stop is a police operation designed to randomly stop drivers to check for impaired driving and other offenses.
In fairness to @CheckStopEdm, they assert on their twitter profile that their service is for people whose blood-alcohol content is below the legal limit to operate a vehicle. I'm not sure that proclaiming your avoid-the-police service is intended only for non-criminals actually helps in any regard, but there you have it.
Someone on Facebook asked the question, if a drunk driver were to read and follow the @CheckStopEdm advice and injure someone on the alternative route would @CheckStopEdm be liable for those injuries?
That is an interesting question, but to me, it's the wrong question. The more immediate question is this: Is publicizing the location of a police check stop, causing a drunk driver to avoid it, an obstruction of a peace officer in the performance of their duties in contravention of the criminal code?
Note that this question doesn't require the drunk driver to hurt anyone. It just requires the drunk driver to exist, and to avoid detection.
There is a case from BC in 1971 in which two undercover police officers were attempting to arrest pan handlers. I apologize, but I don't have a publicly available link to the case. After arresting one pan handler, and being observed doing so, they were followed around as they patrolled the area on foot by two individuals who repeatedly pointed the two police officers out to everyone around as undercover police. Those two were charged with obstruction of a police officer in the performance of their duty.
The judges in British Columbia Court of Appeal carefully considered the history of cases regarding warning people about speed traps, and decided that yes, making yourself an early warning system for an undercover police officer constitutes an obstruction of justice.
The BCCA decided a crucial issue was whether by virtue of the obstructive action the police were deprived of evidence that they would otherwise have obtained.
Extending that logic, if interfering with undercover cops by announcing their presence is obstruction, and warning people who are actually speeding of a speed trap is obstruction, then it seems at least plausible that warning an actual drunk driver of a check stop is obstruction.
These things always depend on the individual facts of the case. I can't say for certain generally, and I remind you that this is not legal advice for any particular person. But if someone came to me saying they wanted to start doing this, I would advise them against it.
Violations of section 129(a) of the Criminal Code carry a punishment of up to two years in prison.