Exact wording of the Edict of Nikaea - Russ wasn't wrong, but Dorn was
*"I see now I have allowed my sons to delve too profoundly into matters I should never have permitted them to know even existed. Let it be known that no one shall suffer censure, for this conclave is to serve Unity, not discord. But no more shall the threat of sorcery be allowed to taint the warriors of the Astartes.* ***Henceforth, it is my will that no Legion will maintain a Librarius department. All its warriors and instructors must be returned to the battle companies and never again employ any psychic powers.***
*Woe betide he who ignores my warning or breaks faith with me. He shall be my enemy, and I will visit such destruction upon him and all his followers that, until the end of all things, he shall rue the day he turned from my light."*
If we are to take the Emperor's words literally, then the Space Wolves and White Scars were truly unaffected by the Edict, as the Rune Priests and Stormseers were not a Librarius, and did not practise warpcraft through the standardised methods taught to Librarians.
I thought that it is also worth noting that Rogal Dorn did not completely abide by the Edict. As per the second sentence of the bolded part above, the Emperor decreed that all Librarians were to be incorporated back into the standard battle companies, but Dorn instead kept his entire Librarius locked up within the Phalanx. In this aspect, he is also guilty of not adhering to the Edict.
Furthermore, if one were to accept the popular interpretation of the Edict completely outlawing not just the Librarius, but all pyschic abilities within the Legions, then the Raven Guard's Mor Deythan units should also have been dissolved, because they were definitely specialised psykers.
EDIT: I think it's important to clarify that the Rune Priests and Stormseers weren't simply Librarians by a different name. The Librarians of the other legions were all trained through a standardised method, taught to access the warp in a specific way, and had the same organisation in their Librarius. On the other hand, the Rune Priests and Stormseers, while definitely warp-wielding psychics, accessed and utilised the warp in a vastly different way from standard Librarians, and had different organisational makeups.