When to use illegal in Korean
Korean: 불법[ bul-beop ]

When to use it
불법 means something is against the law, or not allowed by the law. You can use it for actions like parking, selling things, or downloading files when those actions are not legal. If something is 불법, people should not do it.
Example sentences
여기서 담배를 피우는 것은 불법이에요.
It is illegal to smoke here.
학교 앞에서 불법 주차를 하면 안 돼요.
You must not park illegally in front of the school.
그 가게는 불법 물건을 팔아요.
That store sells illegal goods.
불법 다운로드는 나빠요.
Illegal downloading is bad.
이 강에서 밤에 낚시하는 것은 불법입니다.
It is illegal to fish in this river at night.
여행 중에 불법 택시를 타지 마세요.
Don't take an illegal taxi while traveling.