Russ, this only means быть во власти. The other one is TO BE EMPOWERED (to do something)
Обсуждение (6)
When a judge has a power to prescribe a sentence... would you call it 'власть'? To me, it is more like 'полномочия'. No?
When a judge has THE power to pronounce a sentence, he’s EMPOWERED to do so. We use IN POWER when we talk about governments, elected officials, rulers, presidents, monarchs, etc.
Here are examples in books of how IN POWER is used:
So быть во власти is correct, but the other one isn’t.