In fact, the government's only job is to defend the population and regulate interstate trade. (religion.blogs.cnn.com)
The modeling results also revealed that using a mass - based approach and engaging in interstate trading (to sell excess credits) would be the most advantageous path for Michigan. (aceee.org)
Tariffs are not covered under Article I, Section 8 as you quoted, that sentence applies to only internal interstate trade within the boundaries of the United States. (politics.stackexchange.com)