The subject was ruled off-limits.

规定禁止谈论这个话题。

《牛津词典》

Entire systems are sometimes ruled off-limits because no one understands them; yet these systems still need to be maintained.

因为没有人了解这些系统，所以有时候就使用规则约束禁止进入整个系统；但是仍然需要对这些系统进行维护。

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Well-off families are ruled by calendars, with children enrolled in ballet, soccer and after-school programs, according to a new Pew Research Center survey.

皮尤研究中心的一项新调查显示，富裕家庭的生活是按照日程表进行的，这些家庭的孩子们要跳芭蕾、踢足球、参加课外活动。

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Educators feared that all courses below university level might be ruled off limits to overseas students, even though between 40% and 50% of foreigners at British universities had taken an earlier course in Britain, usually to hone language or study skills.

ECONOMIST: Student visas

Bourgoin were ruled to be off their feet at the ruck shortly after the restart and Steenson stroked home his penalty from 30m out to give Exeter a 9-5 lead.

BBC: Bourgoin 19-34 Exeter

Earlier, a circuit judge had ruled that Harris could cut off the vote recount at 5 P.

FORBES: Top Of The News: Candidates Return To Court