unjustifiable

/ʌnˈdʒʌstɪˌfaɪəbəl/
(of an action 行动) impossible to excuse or accept because there is no good reason for it 不可原谅的；无法接受的；无正当理由的 SYN indefensible
an unjustifiable delay
无理的拖延
OPP justifiable