The Apple website says
http://support.apple.com/kb/HT3920
Summary
Apple will support Microsoft Windows 7 (Home Premium, Professional, and Ultimate) with Boot Camp in Mac OS X Snow Leopard before the end of the year. This support will require a software update to Boot Camp.
so what about Leopard? This seems not so typical of Apple to say something that is quite incomplete... to mention about Snow Leopard and not Leopard -- many people still run Leopard.