In addition to the example given by Michael and quite possibly the most egregious example in the current climate, as it were, of a treaty signature not being followed up by ratification, consider that of the USA and the Kyoto Protocol.
As of July 10, 2006, the USA is listed as having signed Kyoto in 1998 - but has not ratified it.
Here's what Wikipedia has to say:
The United States (U.S.), although a signatory to the Kyoto Protocol, has neither ratified nor withdrawn from the Protocol. The signature alone is symbolic, as the Kyoto Protocol is non-binding on the United States unless ratified. The United States was, as of 2005, the largest single emitter of carbon dioxide from the burning of fossil fuels.. China is projected to take over at the top of the table by 2030.
Although the USA has apparently thought about and looked into how it might go about the unusual if not unprecedented step of legally withdrawing its signature from Kyoto, it appears that it has not done so to date.
To continue with a metaphor that both Michael and I have used, folks who live in glass greenhouses ought to be careful about throwing stones.
It is wrong both in fact and law and seriously misleading for anyone to suggest that Canada has any international legal obligation to ratify the 1996 WIPO treaties. Canada may choose to do so but is not required to do so. Period.