A German court in Hamburg has ruled that the practice of blocking advertising is legal, throwing a wrench into the plans of advertising and publishing giants like Microsoft and Google to stop AdBlock Plus, the highly popular Web page ad blocker.

German publishers Zeit Online and Handelsblatt brought the suit against Eyeo, the company that owns Adblock Plus, which is also based in Germany. The publishers filed suit against Eyeo last December, saying Adblock Plus should not be allowed to block ads on their websites.

Microsoft, Google, and some French publishers were reportedly considering a suit against AdBlock Plus as well, with the chief of a French publisher's association telling AFP that its members lose 20% to 40% of revenue due to AdBlock Plus, which has 144 million users worldwide.

One of those users turned out to be a legal aide to the judge, who wound up becoming involved in the trial. The judge asked the aide, whom he knew to be an Adblock Plus user, whether it was clear to her what she was getting into when she installed Adblock Plus on her device. The woman said that both Adblock Plus's functionality and its whitelist initiative, called Acceptable Ads, were both explained in a clear manner.

"We are extremely happy with the decision reached today by the Hamburg regional court," Eyeo said in a statement. "This is a victory for every single Internet user because it confirms each individual's right to block annoying ads, protect their privacy, and, by extension, determine his or her own Internet experience. It is living proof of the unalienable right of every user to enjoy online self-determination."

The task for Microsoft, et al, has just gotten a lot harder. The German court has set a precedent in stating that users have the legal right to control their PCs and decide what they see when they browse the Web. Now they have to get that precedent overturned before they can take action against Eyeo.

Eyeo is trying to soften the blow with its Acceptable Ads initiative so people can block annoying ads but allow what it deems "decent ads" to come through, allowing for a compromise between users and advertisers.

"Now that the legalities are out of the way, we want to reach out to other publishers and advertisers and content creators and encourage them to work with Adblock Plus rather than against us," Eyeo's Ben Williams wrote on the company blog.

"Let's develop new forms of nonintrusive ads that are actually useful and welcomed by users; let's discover ways to make better ads; let's push forward to create a more sustainable Internet ecosystem for everyone," he added.