There are three areas of law that are relevant to using and sharing open wifi: the responsibility of those use of open wifi, the legal responsibility of those who share their wifi, and ISPs' Terms of Service and open wifi.
Is it legal to use and share your open wifi? This is a question that many people ask once they have gotten further in depth into sharing their own wifi. The simple answer is that it is still somewhat grey, but people are defining the law, in practice, by their behaviors. For example, if you ask people all over the world whether it is wrong to go into someone's house and take things, the vast majority would agree. Even if that house was unlocked and open, and the person taking things was a friend, we would still believe it is stealing.
Now if we ask computer users a question: do you think it is wrong to use a wifi network that your computer has requested permission to access, and to which the router has assigned you an IP, even though you do not have explicit permission of the owner of that network? Most people do this kind of thing, and the vast majority of people try to obey the laws and norms of society. It seems clear that more and more, society believes it is OK to use open wifi. Despite fearmongering in the media, fewer and fewer believe that using open Wi-Fi is wrong, indeed all major operating systems are configured to connect to open Wi-Fi automatically. So while a handful of people still argue that using open wifi is equivalent to trespassing or stealing cable TV, the vast majority disagree, based on their actions.
That said, some courts and states have tried to criminalize using open wifi, with varying levels of success. Here is a recent case that failed:
- Bill criminalizing WiFi leeching shot down, and rightly so, Ars Technica, March 23, 2008
See Wikipedia's article on the Legality of piggybacking
Many large internet companies that provide services, like ISPs, Yahoo, Google, etc. have successfully lobbied to make sure that service providers are not responsible for what their users do. This applies to you too, when you share your wifi. You are a service provider and cannot be held legally responsible for what other people do with your network as long as you are not specifically aiding anyone to do illegal things.
There has been a recent development where people have successfully used their open wifi as an alibi in copyright violation/downloading lawsuits. If you are sued for copyright violation by RIAA or some other company, they have to prove that specifically you broke the law, not that someone using your internet connection did. If you have open wifi, then it becomes very difficult to prove that. If you are interested in reading more, check out the court case Capitol Records vs. Debbie Foster and these articles:
- Woman forces US record industry to drop file-sharing case, The Register, August 3rd, 2006
- Opening Up WiFi Networks To Deny Responsibility, Tech Dirt, May 18th, 2004
- Safe and Insecure, Salon.com, May 18th, 2004
- Judge Awards $68,685.23 in Attorneys Fees Against RIAA in Capitol v. Foster, Recording Industry vs The People, July 16th, 2007
- Scoop: Label Must Pay P2P Defendent's Legal Fees, Listening Port on Wired Blogs, February 6th, 2007
Every internet provider has a “Terms of Service” that you must agree to in order to use their services. These terms include clauses about not abusing the service, the responsibility of the ISP for quality of service, and some include clauses that pertain to sharing wifi. Most ISPs do not allow their customers to resell their internet connections, and some do not allow sharing of their connections. Many ISPs explicitly allow sharing, and they use this freedom to gain customers from the ISPS that have more restrictions. For example, when cable companies started getting into the internet business, they required the customer to pay per computer. This proved quite unpopular with customers, so they changed to charge per location.
We do not advocate breaking the Terms of Service Agreement that you have with your ISP in order to share your wifi. Instead, you should tell your ISP that you want to share, and cancel their service for an ISP that allows sharing (see Wireless-Friendly ISPs)