If not, why? If so, please provide US Federal code, or case law confirming this is the case.
US federal law pertaining to Fraud and related activity in connection with computers suggests that it is unlawful to:
intentionally access a computer without authorization or exceeds authorized access, and thereby obtain
information contained in a financial record of a financial institution, or of a card issuer as defined in section 1602 (n) of title 15, or contained in a file of a consumer reporting agency on a consumer, as such terms are defined in the Fair Credit Reporting Act (15 U.S.C. 1681 et seq.);
information from any department or agency of the United States; or
information from any protected computer;
Whether publicly-served log files are covered is really going to depend upon the information contained in the logs (i.e. if there are requests which include sensitive data) and the definition of "protected computer".
It's generally bad practice to expose log data, however, even if the logs do not clearly contain sensitive information, I'd say it is equally bad practice to go around reading other peoples' logs (even if it's not a criminal offense, you could still run afoul of a civil court if you're somehow using someone else's "semi-private" logs to your advantage).
Comments seem to be primarily focused on the definitions of legal terms and that's far beyond the scope of the answer - the judicial system hasn't figured it out yet, either.