てっそく
ironclad rule; inviolable rule; invariable principle; iron law
Noun
新聞記事しんぶんきじでは、伝聞でんぶん情報じょうほうは伝聞でんぶんとわかるように書かくことが鉄則てっそくだ。
It is a firm rule in newspaper articles that second-hand information is clearly noted as such.