It is not Russia. It is Russian authorities. And they could fine citizens for anything. All Russian laws written in the way that nobody could be alive and lawful simultaneously. And even sometimes not alive too.

So, fines for "unauthorised" use of some technology is not the thing that could prevent use of Starlink in Russia. But the prices and cost of transiever could. Musk could opensource his transievers and allow DIY ones, but something tell me that he would not.