I've heard both claims stated with certainty multiple times. One way to reconcile the contradictions with these statements would be to list and catalogue situations where the gain of power falls into one or the other catalogue. I'm not sure it would satisfy the philosopher in anyone, though.
There's a common law idea that no-one can grant another person a better title than what they have themselves. For example, in any jurisdiction anyone who's selling stolen merchandize isn't a legitimate owner of the items, and can't grant another person the title of an owner. Also, I can't give you the licence to kill nor you can give that licence to me. There's also the idea that people have the power. If an artist creates music that people like, they're able to cash on it, and they're essentially being granted the right to be rich.
One might ask where the powers come from. Not everything is consensual, and the higher powers - or those with the money - haven't probably born that way. Many people hold extrodinary powers without anyone having approved of them. They haven't needed to ask anyone if it's okay for them to take their rights. There are lot of self-determinate people who draw their sense of right and wrong from their own will and ability, and they're less likely to ask approval for their actions, whether that's by law or contracts.
So, I'm saying that there's both kinds of processes in existence. Power is both taken and granted. But, that only begins to explain this situation. Can we get a more satisfying answer for the question about the origins of power?