Non disclosure at the border either way is not advisable if you want to continue crossing in the future. If there is a process you are expected to follow it. I was referring to a Canadian car being driven south and not declaring that to CPB and not having the docs. I have imported US cars to Canada and as per a previous post you notify CPB in advance, surrender US title, and go to Canadian customs to report and pay tax etc.. All that to say make it easy and follow the process.