「on the ground that ～」または「on the grounds that ～」で「～という理由で」という意味になります。
Betty was fired on the ground that she was often absent.
ベティは欠勤がちだという理由で首にされた。
His proposal was rejected on the grounds that it was not practicable.
彼の提案は実行不可能として却下された。
The case was dismissed on the grounds that there was not enough evidence.
証拠不十分を理由にその訴訟は却下された。
He resigned on the ground that he was ill.
病気という理由で彼は辞職した。
He was dismissed on the grounds that he had been negligent in his job.
彼は職務に怠慢だったことを理由に解雇された。