Oh, here's a Wiki on it:

http://en.wikipedia.org/wiki/Kyllo_v._United_States

So, they thermally imaged his home, discovered a huge grow operation, used the thermal imaging to get a warrant (can't do that anymore), and raided his house, caught him red-handed. He fought it to the Supreme Court and they ruled that thermal imaging IS a search, and requires a warrant, then referred the case back to the lower court (so they could see if, absent the thermal imaging, they had enough probable cause to get a warrant). They had basically no other evidence, so Kyllo is now a free man. And thanks to him fighting that case all the way to the top, indoor growers across the U.S. can all breathe a little easier. Seeing as how the raid on his home was ultimately deemed illegal (because of the lack of a warrant before thermally imaging it), I wonder if they had to give him back all his lights and plants. Heh.