这里的 in…form 意思是“以……形式。又如：

We oppose racism in all its forms. 我们反对各种形式的种族主义。

The aim of the civil rights movement was to eliminate racial discrimination in all its forms. 民权运动的目的是消灭各种形式的种族歧视。

网友句子的意思是：

Is it possible to formulate a code of rules for companies which would outlaw bribery in all its forms? 是否有可能为公司制定一套制度从而使各种各样的贿赂行为成为非法？