Darius is correct, but I'd rather see the primary source: Daniel 6.
1 Darius the Mede decided to divide the kingdom into 120 provinces, and he appointed a high officer to rule over each province.
2 The king also chose Daniel and two others as administrators to supervise the high officers and protect the king's interests.
3 Daniel soon proved himself more capable than all the other administrators and high officers. Because of Daniel's great ability, the king made plans to place him over the entire empire.
4 Then the other administrators and high officers began searching for some fault in the way Daniel was handling government affairs, but they couldn't find anything to criticize or condemn. He was faithful, always responsible, and completely trustworthy.
5 So they concluded, "Our only chance of finding grounds for accusing Daniel will be in connection with the rules of his religion.''
6 So the administrators and high officers went to the king and said, "Long live King Darius!
7 We are all in agreement - we administrators, officials, high officers, advisers, and governors - that the king should make a law that will be strictly enforced. Give orders that for the next thirty days any person who prays to anyone, divine or human - except to you, Your Majesty - will be thrown into the den of lions.
8 And now, Your Majesty, issue and sign this law so it cannot be changed, an official law of the Medes and Persians that cannot be revoked.''
9 So King Darius signed the law."
http://www.biblegateway.com/passage/?search=Daniel+6&version=NLT
Daniel fell foul of this law, and subsequent verses tell of his incarceration in the den of lions and his release the next day.
