It's more confusing than ever to know what is legal and illegal for estheticians in spas to perform.
The American Med Spa Association has a list of what is legal and illegal in each state in order for medical spas to be compliant. You can find that information at AmericanMedSpa.org
Generally speaking most radio frequency devices are in themselves illegal. They have not been cleared by the FDA for safety and those that have are only allowed to be used by doctors.
Other illegal services (not a complete list):
-Plasma or Fibroblast treatments (devices are illegal)
-Microneedling over .30 mm (illegal in some states like California)