안 되는 건

what isn't allowed

→ 안
phrase Rare #32,242
what isn't allowed 건 is a shortened form of 것은, meaning “the thing/fact that.” 안 되다 can mean that something is not allowed, possible, or working, depending on context.
KO: 여기서 사진 찍으면 안 되는 건가요?
EN: Is it not allowed to take pictures here?

멀쩡한 놈 빨갱이 만드는 거 아, 왜 그래, 또 무섭게 언론이 거짓말하면 안 되는 건 저도 잘 압니다

Making a perfectly decent guy out to be a commie—oh, come on, don’t scare me like that. I know perfectly well that the media shouldn’t lie.

— Good News (2025)