The GTR forum has some answers. Link:
https://www.gtrlife.com/threads/ecut.../#post-4175966
One of the Q/A from a tuner:
Q- Who is affected?
A- If you have a non USDM ROM file in your car (JDM, Asia, Middle East, Europe, Australia, etc), this does not impact you in any way. Note the change is USDM ROMs. Not "USA Based Tuners", or "Cars in the United States".
If you have an existing tune, this does not impact you in any way.
If your vehicle does not have non emissions compliant modifications, this does not impact you in any way.
If you are starting a new tune in the end of May, your tune will no longer be able to have emissions codes disabled.