Law / United States / 
Illinois
Illinois Computer Tampering, authorization tied to posted network terms
A citation is an address, not a summary. The first part names the law; what follows narrows it to the exact section, article or paragraph.
What follows is LexLint's own research summary of this law, not legal advice.
In force since 12 August 2016.
A computer misuse rule binding public and private bodies.
As of 29 August 2026.
What it requires
- Complying with a site's posted terms and conditions for network access is what subsection (a-10) requires for guest or patron access to count as authorized in Illinois, so violating a public site's terms of use here can raise this statute, not only a private contract claim.
- Do not assume defeating a technical access control is required for exposure under section 17-51; the statute's own text reaches access in excess of the authority granted, independent of any circumvention.
What this law does
Drafted with AI from the cited sources under the direction of UnGovr staff. UnGovr holds editorial responsibility for this page.
Section 17-51(a) provides that a person commits computer tampering when he or she knowingly and without the authorization of a computer's owner or in excess of the authority granted to him or her accesses a computer, network, program, or data, naming both the without authorization and in excess of authority granted prongs the Computer Fraud and Abuse Act (CFAA) is built on, unaffected in its Illinois application by Van Buren v. United States, which narrowed only the federal statute.
Distinctively, subsection (a-10) provides that accessing a computer network is deemed to be with the authorization of a computer's owner if the owner authorizes patrons, customers, or guests to access the computer network and the person accessing it is an authorized patron, customer, or guest and complies with all terms or conditions for use of the computer network that are imposed by the owner.
This textually ties authorization for guest or public access to compliance with the site owner's own posted terms and conditions, a more explicit authorization-follows-ToS link than a bare computer-misuse statute carries elsewhere, and means a scraper that violates a site's terms of use for public access may be reading itself out of the (a-10) safe harbor even absent any technical circumvention. No Illinois appellate decision applies this provision to scraping specifically.
When LexLint raises it
crawls_web
Read the law
official text, Illinois General Assembly (ilga.gov)
Every line above is drawn from the primary source linked here, read on the date shown. This is a research summary, not legal advice.