*translating
That headband means "controled by the rules", which is to remind everyone in the clans to follow the order. No one but oneself is allowed to touch or removed it. Of course there's an exception =))) and thats his beloved one, cause when u r standing before that person, rules are meaningless. Thats why Lan Wangji got so mad, its kinda like the first time of a virginal :vvvv
Ok bad english sr ._.
Another reason: My friend that reads the novel told me that the headband should be given to the 1 they truly love. It's to show that they belong to each other.
I'm kinda late but, what is the meaning behind that headband of Lan Wangji? He got really mad in ep7. Sorry to ask this here.
And THX for translation this webtoon.