In Illinois it is specifically a criminal act to violate the terms of service of a web site under the Computer Tampering law:

(720 ILCS 5/17-51) (was 720 ILCS 5/16D-3) Sec. 17-51. Computer tampering.

https://www.ilga.gov/legislation/ilcs/ilcs4.asp?DocName=0720...

(it starts as a misdemeanor, but rises to a felony if you do it multiple times)