I found a pretty good research paper back from 1997 describing the old Filipino system of of citizenship based taxation and the impact of the Canada Philippines Tax Treaty. Like the US Canada Treaty the Filipino treaty had/has a “savings clause” allowing the Philippines to tax its citizens living in Canada on Canadian source income. The paper suggests a route to bringing a charter challenge to get the treaty thrown out on the basis of equality of citizenship (something we have talked a lot about here). This is big very big. I am going to try to track down the author of this paper.
Double taxation: Riding on the backs of Filipino export labour, by Genevieve Hamada-Plank , Ottawa Law Review / Revue de droit d’Ottawa 29 (1997-98) 395-423.