Their environmental policy was revised to operate in accordance with the new regulations.

in 是介词，表示"在...方面"或"以某种方式"。 accordance 是名词，来自动词 accord（一致、符合），意思是"一致、符合"。 with 是介词，表示"与...一起"或"伴随"。 in accordance with 是一个固定短语，意思是"依照、按照"，表示遵循某种规则或标准。