Orbanski v. the Queen, Supreme Court of Canada, June 16, 2005 [ruling that police at roadside DUI checkpoints do not have to inform suspects of their right to legal counsel before asking them whether or not they had been drinking or requesting them to perform sobriety tests]. Excerpt:

Screening drivers necessarily requires interaction with motorists at the roadside. The scope of justifiable police conduct will not always be defined by express words found in a statute but will sometimes depend on the purpose of the police power in question and the particular circumstances in which it is exercised. It is therefore inevitable that common law principles will be invoked to determine the scope of permissible police action. Here, the roadside screening measures used to assess the sobriety of O and E — the request to perform sobriety tests and the question about prior alcohol consumption — were reasonable and necessary for the police officers to fulfill their duty. These measures fell within the scope of authorized police actions and were incompatible with the exercise of the right to counsel.

Read the full text of the opinion here. Reported in JURIST's Paper Chase here.