Tesla only has showrooms. Their stores are pretty much the same everywhere. There are no cars you can buy and drive off in.
In states where Tesla can sell direct to consumers, the showroom has sales people who can talk to you about buying a car, and sit next to you to answer questions as you do so at teslamotors.com.
In other states, the showroom does not have sales people. The staff can answer questions about the car, but not about purchasing (pricing, financing, etc). If you want to buy one, they direct you to visit teslamotors.com.
In no case are people in a state prevented from buying a Tesla car. The buying experience is the same everywhere: go to teslamotors.com, configure and order a car, and either pick it up or have it delivered to you after it's been manufactured.
As for the legal aspect, the federal government does have the ability to regulate interstate commerce, and federal law preempts state law. When there is no federal law, however, the states are free to regulate in that area. If Congress were to enact a law guaranteeing the right of manufacturers to sell direct to consumers, this would preempt the state laws prohibiting it, and Tesla could have sales people in all its showrooms. IANAL.
You're largely correct, but there are some pretty substantial differences in the experience.
First, Tesla does actually have some cars you can just buy and go. They're (currently?) the minority, but they're there. They're starting to sell used Teslas, and they also have "inventory cars" which are showroom, test drive, and loaner cars which have finished their corporate service and are ready to be sold.
Second, test drives are pretty key to the whole process (even if you can't test drive the specific car you buy, most people want to test the model) and even that gets caught up in this whole nonsense. Until recently, you couldn't even get a test drive in Virginia. I had to go into Maryland to try one out. Tesla had a showroom in Virginia but they couldn't even let you drive one, let alone sell you one.
Third, in states where they are allowed to sell, you can configure and purchase on site rather than online. The effect is the same, and they're basically just punching the order into the computer for you, but for people who prefer buying from a real person it can matter.
Fourth, taxes and registration are different depending on how you bought it. When I bought mine in Virginia, I had to take delivery in Maryland, and the sale was actually processed in DC. I had DC temporary tags, and I had to handle Virginia registration and pay Virginia sales tax on my own at the DMV. Now that they can sell directly in Virginia, they can handle registration and sales tax themselves, which saves a decent amount of hassle.
Finally, it can affect the post-sales experience in extreme cases. For example, New Mexico is so strict about this stuff that they won't even let Tesla open a service center. You can buy one there, but you'll have to go extremely out of your way to get it serviced.
In states where Tesla can sell direct to consumers, the showroom has sales people who can talk to you about buying a car, and sit next to you to answer questions as you do so at teslamotors.com.
In other states, the showroom does not have sales people. The staff can answer questions about the car, but not about purchasing (pricing, financing, etc). If you want to buy one, they direct you to visit teslamotors.com.
In no case are people in a state prevented from buying a Tesla car. The buying experience is the same everywhere: go to teslamotors.com, configure and order a car, and either pick it up or have it delivered to you after it's been manufactured.
As for the legal aspect, the federal government does have the ability to regulate interstate commerce, and federal law preempts state law. When there is no federal law, however, the states are free to regulate in that area. If Congress were to enact a law guaranteeing the right of manufacturers to sell direct to consumers, this would preempt the state laws prohibiting it, and Tesla could have sales people in all its showrooms. IANAL.