The law changed in 2018 due to a SCOTUS opinion. Here's a link to the case:
https://www.supremecourt.gov/opinion...7-494_j4el.pdf
Basically, this is how things are:
1. A State can now require an out-of-state internet seller who sells retail goods to consumers in that State to collect the sales tax that an in-state brick and mortar retailer would charge that consumer for the same transaction. A certain level of "nexus" is required, e.g., $100,000 in sales per year or 200 transactions per year.
2. State must first pass a law which allows the State to tax such "remote seller" transactions and require the seller to register with that State, file returns, etc.
3. Some States have already done this. Others will likely follow.
It is more complicated than this, but this is the essence.