[gamblor956]

The P&I clause simply means that states can't discriminate against people from other states. This was explicitly clear in the original (Articles of Confederation) version of the clause, which stated that citizens of one state traveling to or doing business in other state were "subject to the same duties, impositions, and restrictions as the inhabitants thereof."

This means, for example, that if a state wants to tax residents of other states that do business in their state, they have to tax their own residents for the same activities.

So, if CA wants to tax an Illinois business for its activities in CA, it would have to tax CA residents for those same activities. And CA absolutely does.