Your comment got me thinking. I haven't brushed up on this kind of rule in a long time. A quick read of the driver's handbook says a solid line means it is unsafe to pass but doesn't say anything about it being illegal to pass. If something bad happened, I assume you would be found to be at cause if you were passing on a solid line.

I found a link to the Ontario Highway traffic act that doesn't say anything about solid lines.

Passing vehicle going in same direction

(8)  No person in charge of a vehicle shall pass or attempt to pass another vehicle going in the same direction on a highway unless the roadway,

(a) in front of and to the left of the vehicle to be passed is safely free from approaching traffic; and

(b) to the left of the vehicle passing or attempting to pass is safely free from overtaking traffic. R.S.O. 1990, c. H.8, s. 148 (8).

Driving to left of centre prohibited under certain conditions

149.  (1)  No vehicle shall be driven or operated to the left of the centre of a roadway designed for one or more lines of traffic in each direction,

(a) when approaching the crest of a grade or upon a curve in the roadway or within 30 metres of a bridge, viaduct or tunnel where the driver's view is obstructed within that distance so as to create a potential hazard in the event another vehicle might approach from the opposite direction; or

(b) when approaching within 30 metres of a level railway crossing. R.S.O. 1990, c. H.8, s. 149 (1).

In short, it appears that a solid line in Ontario is at best a visual aid to determine whether you are approaching the crest of a grade or upon a curve (and the rest of the stuff in 149a).