It is not difficult for a crown prosecutor to respect the criterion in section 253 of the present Criminal Code that allows a judge to convict someone for impaired driving once the judge is convinced that the person consumed alcohol and notes certain symptoms, which incidentally are not the clearest. According to the Supreme Court's interpretation, this can be a minimal difference that affects a person's driving.
For parliamentarians here, note that there might not be much to distinguish a minimal difference from impairment of any degree, but this difference is huge in practice.