Where does it say it's banned?

Second paragraph mentions "regulatory restrictions".

Clinuvel Pharmaceuticals intended to offer it as a cosmetic, but abandoned this pursuit in the 2000s due to regulatory restrictions and concerns about the promotion of suntanning. Unlicensed Melanotan II is found on the internet, although health agencies advise against its use due to lack of testing and regulatory approval.

It’s banned for cosmetic use. You can still buy it as a “research chemical”.