A couple of years ago I was helping a friend with a large boat he had bought in Newfoundland. We flew up there a couple of times and no problems at the airport. Then I drove up there in a one ton van loaded with parts and tools. I went across the border in northern Maine. I was asked if I had ever been arrested and said no even though I had been. I didn't know they did a background check and when the immigration agent, a rather nice young lady, came back and asked me about the arrest I explained that, yes, I had been but no charges were filed and so I didn't think it would matter. She was nice and said I could go on after a brief search of the van. I drove on up and unloaded the van and returned to Portland Maine to pick up my friend who had flown up. When we tried to reenter Canada a different agent, again a woman but this one seemed to have a chip on her shoulder, refused me and since my friend had been arrested a number of years earlier for a DUI he was deemed an undesirable also and refused too. When we talked to the US customs agents they said the Canadians were very unpredictable about how they treated those trying to enter.