If you are a corporation/member of the government and/or enforcing agencies, then there are a lot of laws that you can leverage to prosecute. If you are a hacktivist then you should be aware of these laws and understand the consequences of breaching them.
Digital Millennium Copyright Act: stipulates that publishing details of vendor DRM controls is illegal. This is stupid as it stops people from revealing stupid DRM techniques.
Foreign Intelligence Surveillance Act: a ‘secret’ court that grants government requests for surveillance
Communications Decency Act 1996: you can’t send ‘prohibitive’ material to persons under the age of 18 years old (I think this was thrown out)
Child Online Protection Act: restricts minors to access ‘prohibited’ sites like drugs, porn etc. (I think this was thrown out too)
Child Internet Protection Act 2000: primary schools and libraries have to use filters (proxy servers to block dodgy content)
Communications Act 1934: consolidated a bunch of acts before into a single one (radio and telephone)
Telecommunications Act 1996: the first overhaul of telco law in a long time
Electronic Communications Privacy Act: modifies Extended Wiretap Act to allow for wireless tapping
Computer Fraud and Abuse Act 1986: it’s a crime to break into any computer basically. This was the act used to prosecute: Robert T Morris, Bradley Manning, and Aaron Swartz.
The USA Patriot Act 2001 – this came out just after 9/11 when Americans were scared. Consequently this law gives the the enforcement agencies: NSA, FBI, police a lot of power to do what they want without even asking for it at court. The NSL’s (national security letters) are a part of this.
NB: The Above Is American Law. I will do another one for Australian Law.