What does Daniel 6:12 mean?

They went straight to the king and asked, 'Didn’t you sign a law that for thirty days anyone who prays to anyone except you would be thrown into the lions’ den?' The king answered, 'Yes, that’s the law, and it can’t be changed.' Daniel 6:12 - Modern Text Bible

(They remind the king of his own law, making sure he can’t back out.)