Banning is counterproductive for cults. It feeds into the persecution complex. Those under cult indoctrination will dig in further.
Russia's banning of JWs is a win/win for Watchtower. They get to play the Persecution Card which validates the belief system. It also feeds into the whole "the end is so close" and attack by the "king of the north" hype, which also ends up being validating. JWs in all other parts of the world, who might've been on the verge of waking up and freeing themselves, will be scared back into "mother's arms".
Removing tax exemption and/or financial penalties targeted at the organization are the best stick. The answer is not penalizing individual JWs, who become victim twiceover, both of an authoritarian religion and an authoritarian government.