IT IS NOT A LAW
"Legally, the question has revolved around a "physical presence" requirement that was reached in a 1992 Supreme Court judgment (Quill Corp v North Dakota). Under that decision, it was mandated that sales tax obligations could only be applied to companies that were physically based in the state. But that was before the internet took off and the states are arguing that the law should no longer hold."
Supreme Court decisions are not laws, but opinions based on the Constitution, federal laws, and legal precedents. The US Constitution says that each state has a measure of sovereignty. In other words, the laws in Hawaii do not apply to people who are not in Hawaii and not residents of Hawaii. And even then, not every law is enforceable on the residents of Hawaii while they are out of the state. If I am in Montana I am not bound by Hawaii's maximum speed limit even if I am resident of Hawaii. These are just simplified examples.
There is no federal law on state sales tax. Sales tax part of a state's budget, which is actually a law. And that law is only applicable within the borders of the state that has that law. If a business has no presence of any kind outside, then that state cannot enforce the sales tax law. Suppose My Widget Co. only had a warehouse in Florida. Then California has no right to force me to collect sales tax because there is no federal law saying I must, although there is a legally binding opinion saying I don't have to. I am not in California, I do not have a presence there, you cannot compel someone (and in US law, businesses are a someone) to follow your laws if you are completely outside their borders. It is a bit like the US trying to force its laws on Canada. They try, but it ain't right.
What you are supposed to do is pay a use tax. But it is political suicide to shakedown your citizens. It is a lot easier to shakedown big business. This does not fix the ultimate problem: sales tax laws are confusing. In my state, there is a lower rate for food, there is a state rate, then some counties adds some on top, and then some cities add a little more too. How can a business determine which address has to pay which rate? If you go by the zip code, you must remember that the zip code is just the identification of the post office that delivers your mail. So I live in the city and pass the city rate, but 1 mile away another person is outside the city limits, same zip code. 10 miles away, a zip code spans into 3 different counties, albeit not by much. This becomes complicated real quick.
The simple fix is to pass a federal law that simply states business may only pay the base state rate; they may not pay the county or city additions. And each state must provide an easy way to send payments. If the state needs to audit a business, then a state representative must travel to that business and may only see the dollar amounts, and not the actual invoices, of purchases within that state. Penalties may not be assessed. It must be easy for businesses to comply.