Yes they can stop you - but to say it's routine sounds wrong - I will admit I haven't driven across the border in a long time, but when you head to the US, you

Yes they can stop you - but to say it's routine sounds wrong - I will admit I haven't driven across the border in a long time, but when you head to the US, you don't normally deal with canadian border authorities, and vice-versa - you juts deal with the authorities of the country you are entering, not the one you are leaving.