null and void
adjective [ after verb ] law uk/ˌnʌl ənd ˈvɔɪd/ us/ˌnʌl ənd ˈvɔɪd/
无法律效力的
having no legal force
The change in the law makes the previous agreement null and void. 法律变更致使之前的协议失去了约束力。
The election was declared null and void. 这次选举被宣布无效。