According to a (new) law, all providers of tools to spread information (or something like that) must be registered in a special list (and while it is a law, there are only 90 sites there, while theoretically over 9000 should be registered or banned).
At first sight registration means nothing - you are giving you name, your site or product and a email to contact you if something happens.
BUT according to another law, every such provider will have to store 6 months of every bit of user's traffic + give all the information FBR wants.
1. So the main guy in RKN (organization that blocks "illegal sites" etc) asked Telegram to register, Durov said nothing for a month
2. The guy: plz register, or you will be banned
Durov: no. (and meanwhile new beta update - telegram will have proxy on mobile too)
3. All the main TV channels began to show "drugs, terrorist groups, all the attacks are planned through telegram" etc etc
4. That guy: plz register or be banned in a few days
Durov: no, we won't give you users' data and / or traffic etc
That guy: no, we don't ask you to give us users' data, just register and that's all
(remember, that there are laws that would force providers to store / share that info)
5. Durov: oh, if you just want us to register, you can the details, they are public, but we won't obey the laws about storing and sharing info anyway
That guy: okay.
So. Telegram is not banned yet, because it was supposed to be banned just because it is not registered. But being a registered unit, you must obey Yarovaya packet thing (storing and sharing 6 months of traffic). And when FBR will ask for the info, and Durov will say "no", Telegram will be banned.