〜を禁じ得ない
can't help (feeling), can't hold back
Emotion noun (涙, 怒り, 同情, 驚き) + を禁じ得ない
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を禁じ得ない means "can't suppress a feeling": 彼の話を聞いて、涙を禁じ得なかった, "hearing his story, I couldn't hold back my tears".
The noun is an emotion or its sign: 涙, 怒り, 同情 ("sympathy"), 驚き, 憤り ("indignation"), 失笑 ("laughter"). It's usually a reaction to someone else's situation or behaviour.
It's literally "can't forbid (the feeling)", and it's very formal, found in editorials, speeches and statements. The everyday equivalent is ずにはいられない (N2): 泣かずにはいられなかった.
Don't confuse it with を余儀なくされる, "be forced to do", which is about actions, not feelings.
Examples
彼の話を聞いて、涙を禁じ得なかった。
Hearing his story, I couldn't hold back my tears.
その判決には、怒りを禁じ得ない。
I can't help feeling angry at that verdict.
被害者の話には、同情を禁じ得ない。
I can't help feeling for the victims.
彼の無責任な発言には、驚きを禁じ得ない。
I can't help being astonished at his irresponsible remarks.
事件の残酷さに、憤りを禁じ得ない。
The cruelty of the crime fills me with indignation.