A good TL;DR from my co-worker at the Tax Foundation (https://twitter.com/jbhenchman/status/1009808187137150977):

Does your state online sales tax law have:

* Safe harbor for sellers who have limited activity

* No retroactivity

* Adheres to SSUTA

* State level admin

* Provides software

* Provides immunity for errors

If so, upheld. If not...