U.S. Customs clears all passengers who boarded trains in Canada when they arrive at Skagway. There is a Canadian Customs station at Fraser B.C. All the people who ride the train from Skagway to Fraser and then bus to Whitehorse clear customs there after leaving the train. The people riding by train from Skagway to Bennett are reported to Customs by the Conductor northbound but are generally not interviewed by the Fraser Customs Officer. Any hikers who board at Bennett and ride back to Skagway have to clear Canadian Customs at Fraser and U.S. Customs at Skagway.
In the old days Canada maintained a Customs Officer at Carcross who rode to Bennett on the train every day to clear all the northbound passengers and the people riding Skagway/Bennett/Skagway.