Is a fire protection bylaw retroactive or otherwise?

It is clear enough the purpose of the bylaw was for the preservation of life and property from fire, and the municipality is given the power to pass bylaws for such purpose by s. 156 (supra). The appellants submit, however, that as s. 171 of the bylaw applies to existing buildings, it is retroactive and thus is not authorized. In my opinion it cannot be said that the bylaw is retroactive. The distinction between retroactivity and interfering with a property right is set out in West v. Gwynne (1911) 2 Ch. D. 1 where at p. 11 Buckley L.J. said, "Retrospective operation is one matter. Interference with existing rights is another. If an Act provides that as at a past date the law shall be taken to have been that which it was not, that Act I understand to be retrospective. That is not this case. The question here is whether a certain provision as to the contents of leases is addressed to the case of all leases or only of some, namely, leases executed after the passing of the Act."