You're missing what I'm saying. When she says "It's against the law", she's not saying it's against the law to use anesthesia on a villain, she's saying it's against the law for CREATI to use anesthesia on a villain. Because she's not a licensed hero. It's against the law for her to be fighting ANY villain without special permission.
That's why Midnight is telling them to do it anyway.
The situation being dire doesn't magically make it legal. It's STILL illegal. It's not like they're acting in self-defense. Midnight is actively sending them to engage Gigantomachia.
She might get in trouble for it later, but the situation is such that she's willing to suffer that punishment later.
It's also possible the law will look the other way, like they did with Stain. But, again, that still doesn't make it legal.