you know that the info the canadians are using to keep people out of the country is straight from the FBI database. part of some happiness & security agreement. it is only supposed to be sued to screen for terrorists, drug runners, and sex criminals, not for people with DUIs, shoplifting raps, or even protest arrests; however the canadians are using it very loosely. the US would like to expand this arrangement with other countries, which would in effect keep a large number of people from leaving the US. though it would be the US's doing, they could blame it on the country denying it. oh yeah, and police records are pretty much secret, so you have no idea what is in your record or if the information is correct. yes, theoretically you do have access to your police file but you need a lawyer to get to it. the canadians are under no obligation to tell you what they see on the screen as we are trying to get into Canada, which isnt our country. a friend of mine used to say, "the more russia becomes like america, the more america becomes like russia." welcome to the ussr.
It works exactly the same both ways. If you're a canadian with a dui, shoplifting, or protest arrest record, they can deny you entry into the states.