harry potter - Why isn't the Memory Charm (Obliviate) an Unforgivable Curse?

There are three Unforgivable Curses:

• The Killing Curse (Avada Kedavra): Kills someone


• The Cruciatus Curse (Crucio): Causes pain


• The Imperius Curse (Imperio): Controls their will

But what about the Memory Charm (Obliviate)? Despite its label as a charm, shouldn't it be classified as an Unforgivable Curse?

We see them quite clearly in Chamber of Secrets where by Lockhart's own admission, it has the power to make someone lose their minds:

'The adventure ends here, boys!' he said. 'I shall take a bit of this skin back up to the school, tell them I was too late to save the girl, and that you two tragically lost your minds at the sight of her mangled body. Say goodbye to your memories!'

He raised Ron's Spellotaped wand high over his head and yelled, 'Obliviate!'

Harry Potter and the Chamber of Secrets - p.224 - Bloomsbury - Chapter 17, The Chamber of Secrets

As Au101 wrote in this answer about why Gilderoy Lockhart couldn't recover from his backfired Memory Charm:

"'Say goodbye to your memories!'" There's no talk of wiping out the last 24 hours or anything like that. "[Y]ou two tragically lost your minds", he's not just gonna do enough to get away with it.

Wiping someone's mind permanently seems like a short step away from outright killing them. And even if they don't completely wipe their mind, it seems like a huge personal violation to tamper with another person's memories. You could make them forget something really precious to them (e.g. the day they met their spouse) or some harm that was done to them (e.g. abuse).

Given all of this, why isn't the Memory Charm (Obliviate) an Unforgivable Curse? Or for that matter, why isn't it regulated at all?

Answer

It's not an unforgivable curse because it's a standard spell, used all the times by the wizards who have to deal with muggles witnessing magic.

‘It’s like some sort of … I dunno … like some sort of rally,’ said Mr Roberts. ‘They all seem to know each other. Like a big party.’ At that moment, a wizard in plus-fours appeared out of thin air next to Mr Roberts’s front door. ‘Obliviate!’ he said sharply, pointing his wand at Mr Roberts. Instantly, Mr Roberts’s eyes slid out of focus, his brows unknitted and a look of dreamy unconcern fell over his face.

^{Goblet of Fire}

They are even called Obliviators

Arnold Peasegood, he’s an Obliviator –member of the Accidental Magic Reversal Squad, you know … and that’s Bode and Croaker … they’re Unspeakables …’

^{Goblet of Fire}

Indeed in Halfblood Prince there are entire teams out there responsible for maintaining secrets

Fudge grimaced. ‘He used giants last time, when he wanted to go for the grand effect. The Office of Misinformation has been working round the clock, we’ve had teams of Obliviators out trying to modify the memories of all the Muggles who saw what really happened, we’ve got most of the Department for the Regulation and Control of Magical Creatures running around Somerset, but we can’t find the giant –it’s been a disaster.’

^{Halfblood Prince}

It should also be noted, although Crouch authorises the use of unforgivable curses during the first war, this can be linked to martial law during WW2, emergency situations can lead to normal laws being relaxed or set aside.