Nothing is banned at all at least! Except for some strict regulations placed by social media platforms as well as Google ads on those who may want to advertise their ICOs.

I really do not see any challenge in this as even during all these period that it was halted shortly, a lot of ICOs were still able to push their projects out to the world, which makes it that simple that once you have a brilliant idea, there are other effective medium that can be used to push them out than social media or Google ad.