SAN FRANCISCO — Toss together Alex Kozinski and an untested computer-crime statute, and you can imagine the result.

At oral arguments before an 11-judge panel on Thursday, the Ninth Circuit chief judge repeatedly challenged the Justice Department’s position on the scope of the Computer Fraud and Abuse Act — a position that could lead to the criminalization of seemingly innocuous computer activity, like providing false information on Facebook or in violation of terms of use agreements or using work computers in violation of employer policies.