In order to have a successful meeting with a reasonable chance for world peace you need in attendance, world leaders that actually want peace. Which automatically excludes NATO membership countries. Remember when NATO used to be a defensive pact?
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As far as Canada goes you can't say you want peace and at the same time, be selling military equipment to countries currently at war. It was only a few days ago that yet ANOTHER school in Yemen was bombed by Saudi Arabia. 
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Aren't we sick of the hypocrisy yet? But, I thought we took Canada back!