'According to the Law' in the Bible

The drinking was done according to the law, there was no compulsion, for so the king had given orders to each official of his household that he should do according to the desires of each person.

“Go, assemble all the Jews who are found in Susa, and fast for me; do not eat or drink for three days, night or day. I and my maidens also will fast in the same way. And thus I will go in to the king, which is not according to the law; and if I perish, I perish.”