Not exactly. The dealership is licensed in the state as an official agent of the automaker and is subhect to the states jurisdiction.
Can the CA legislature dictate than no car can be sold in the state of CA unless it came off an assembly line located in the state, and the corporate headquaters of the company building them is located in, and paying their state income taxes to the state of California?
Sure. But that doesn't mean that the auto makers will comply, and, as green as the left coast is - I doubt the people would be happy if no new cars could be sold in the state because of some silly act of thier legislature...
If California can do that with cars, or anything else, what will be the effect on interstate commerce if they do it, and then other states follow suit to protect their own industries and tax base?
Obviously this would be suboptimal (LOL). However, as it would be insane for almost any major manufacturer to have plants "everywhere" - it would likewise be insane for states to begin making such laws! 200 years ago perhaps, since most things NEEDED to be produced locally as the cost and risk of transport was too expensive.
I contend that a broad definition of what the commerce clause to allow regulation of intrastate is the exact opposite of it's original intent as it gives the Federal Government the power to regulate - theoretically - all the way into you bedroom.
I agree the "substantial effects" doctrine needs to go, but I still contend that the original intent of the Commerce Clause would disallow a state imposing an embargo for the same reasons it would disallow imposing an import tax, duty, or tariff. The are all equally destructive to interstate commerce.