Grammar › N1 · 03 Reasons and causes
〜とあっては: if it is a case of ...; given that
N1 · 03 Reasons and causes
Says that in a special situation, one can't act otherwise.
Noun or plain clause + とあっては. The first part is a serious condition (a boss's order, a favor), the second part says "I must/cannot". Compare 〜とあれば, which is willing; this one is more "no choice".
Examples
恩人の頼みとあっては、断るわけにはいかない。
Since it is a request from my benefactor, I cannot refuse.
社長の命令とあっては、従うしかない。
Given that it is the president's order, I have no choice but to obey.