"Lawful demand" refers to a request or order made in accordance with the law. It means that someone is asking for something in a way that is legal and within their rights to do so. Full definition
First, the evidence must establish that an officer made a lawful demand on you to provide a sample of your breath. (yourlegalbutler.com)
258 (1)(c) and 258 (1)(g) of the [Criminal] Code does not support the requirement of a lawful demand for the evidentiary shortcuts to apply,» Justice Michael Moldaver wrote, with Justices Andromache Karakatsanis, Richard Wagner, Clément Gascon and Suzanne Côté concurring. (canadianlawyermag.com)
The trial judge in the case found that the grounds to make the breath demand were insufficient, but he applied Rilling, which held that it is unnecessary for the Crown to prove a lawful demand in order to rely on the evidentiary shortcuts. (canadianlawyermag.com)