 So what has happened in the past is people end up in the gym of not having proof of vaccinations, so therefore they can't cross the border, pick their dog up, and take it back home with them. U.S. Senator Susan Collins is asking the U.S. Centers for Disease Control to postpone implementation of the new rules. She says it could keep some Canadian mushers from participating in the Can-Am Crown international sled dog race in Fort Kent, a major economic driver for the region.