Delta 8 THC is NOT illegal.
There has been a great deal of misinformation and misunderstanding about delta 8 THC. The DEA confirms that delta 8 made from hemp materials is not subject to the Controlled Substances Act.
There are ultimately two main requirements for a Delta 8 product to be legal under the definition of hemp:
It must be derived from hemp (again, naturally or synthetically produced from cannabis materials is legal; but synthetically produced from non-cannabis materials is illegal).
It may not contain more than 0.3% Delta 9 THC.
The DOJ-DEA letter, in its entirety can be found here: DOJ-DEA Letter Regarding Natural Hemp-based THC Materials