expression
out of the question; preposterous; absurd
Strongly dismissive expression used to reject something as completely unreasonable or unthinkable. Often used in formal or emphatic contexts.
そんな要求は沙汰の限りだ。
Such a demand is out of the question.
彼の提案は沙汰の限りと言わざるを得ない。
I have to say his proposal is preposterous.
とんでもない is a common casual expression for 'outrageous' or 'unthinkable'. 沙汰の限り is much more formal and stronger in tone.
沙汰 originally referred to official communication or judgment, and 限り means 'limit' or 'extreme'. The phrase literally means 'the limit of what can be discussed or judged', implying something so unreasonable it cannot even be considered.