A while back, AT&T took Microsoft to course over Windows. They claimed that their copyrights were infringed upon, due to Windows support of certain speech compression systems. AT&T's intent was to collect a royalty on every system sold with Windows, regardless of where it was in the world. Despite Microsoft being U.S. based company, however, the Supreme Court has decided that Microsoft is not liable for anything outside the border. In that fashion, they'll save a lot of money in royalty costs, and it could impact how much they pay out to other companies around the world for patent disputes.

For Microsoft, this could help them a lot in other countries they are fighting. If they don't have to worry about U.S. regulation in other countries, it'll open the door for many business practices they can't get away with normally.