to remove a formal or official title or description from a person, an organization, etc., usually so that they no longer have the right to do something

They filed a petition with the National Labour Relations Board as the first step towards trying to decertify the union. 他们向国家劳工关系委员会提交了一份请愿书，作为试图取消工会认证的第一步。

The board decertified the farming operation as organic. 董事会取消了该农场的有机认证。

to say that someone is no longer qualified (= officially agreed to have the necessary skills) to do a particular job, taking away their legal right to do it

If an air traffic controller is decertified they must go through retraining and be recertified. 空中交通管制员如果被取消资格，则必须经过再培训才能重新获得资格。