15 Then the men went as a group to King Darius and said to him, “Remember, Your Majesty, that according to the law of the Medes and Persians no decree or edict that the king issues can be changed.”

Read Daniel 6:15 Using Other Translations

Then these men assembled unto the king, and said unto the king, Know, O king, that the law of the Medes and Persians is, That no decree nor statute which the king establisheth may be changed.
Then these men came by agreement to the king and said to the king, "Know, O king, that it is a law of the Medes and Persians that no injunction or ordinance that the king establishes can be changed."
In the evening the men went together to the king and said, “Your Majesty, you know that according to the law of the Medes and the Persians, no law that the king signs can be changed.”