right authors, wrong book. The two of them had aliens conquering Earth (or trying to - we beat them with a kick ass project Orion based "big dumb booster" with attitude) in Footfall. Pournelle wrote the chapter about how the aliens (looked like baby elephants with trunks that split into 8 "digits") defeated the Kansas militia (the chapter was title "The Jayhawk War") using the flying crowbars from Pournelle's days advising President Reagan. His other little contribution came to be called "Star Wars" by it's critics.
The aliens in Footfall used the space rocks for more spectactular impacts, such as wiping out life in the southern part of the continent of Africa. That was the "foot" in the title. Good book.
The whole "chairman of the council" bit is a little dated. According to Niven they haven't met in about 20 years. Almost all the meetings took place at Niven's house, by the way. I spent a long drunken weekend with the two of them at a Con here in Memphis about 20 years ago. Fun guys. I would run into Jerry Pournelle almost every year at Comdex following that and he'd remember me, which was flattering. He wouldn't, however, remember what we did while we were together, so he'd always ask me not to mention anything to his wife, just in case (g).