First, a bit of background.
Let's say there are two real ways to power your magic in this world. For the sake of the question, I'll refer to them as "light" and "dark". Both kinds of magic are capable of the same results, at the same power. The question is about their allowed use.
"Light" magic only uses your own reservoirs of energy (let's call it "mana", for the sake of the argument) and is considerably more expensive to cast, mana-wise.
"Dark" magic is considerably less expensive to cast, but this is due to the fact it pulls on all the mana of everything around you when you cast it.
Everyone has different levels of mana, and as such has different amounts per day. A loss of all your mana doesn't result in death, it just means you can't use any magic until your mana reserves naturally replenish over time. There is a caste-based, very religious society that completely forbids use of Dark magic, as they see it as a violation of individual sovereignty - You're using someone else's mana without permission. As such, all use of Dark magic, no matter what the reason, is explicitly forbidden in this society.
Knowing that these people naturally tend towards systems of very defined order, what kind of society would allow use of Dark magic in this context? Clearly an anarchist would likely have no problem using it, but I'm looking for an ordered society that accepts the use of such magic, partially or completely. What kind of government would allow it? Would a religion?
Clarifications: Spells can pool the mana of everyone collaboratively casting it, to cast stronger spells, if everyone willingly contributes their own mana via "light" magic. Two "light" magic users could use their mana together to cast, but it's something willingly given, rather than taken by "dark" magic. Protecting your mana from someone else's use is extremely difficult. Such a shielding spell is something that would require a massive mana base to create even a temporary shield on a single target or area. This makes such shields rather unfeasible for anyone's use other than effectively a King or the Pope.
Edit 2: Based on feedback, I think 'shielding' is something that needs to be relatively cheap and easy in this world, otherwise 'dark' magic becomes more rampant. Thanks for the discussion, everyone! I believe this has been answered sufficiently.