Last week an Ecuadoran appeals court upheld an $18 billion ruling against San Ramon-based oil giant Chevron for pollution and ill health effects caused in the country's rainforest. The decades-old damage stemmed from oil exploration by Texaco, which Chevron bought in 2000.Lawyers on both sides of the lawsuit clashed yesterday on KQED Radio's Forum program. Also on the program was Patrick Radden Keefe, an author and journalist who has written a piece on the case appearing in the latest issue of The New Yorker...On Forum...Radden Keefe explained the difficulty plaintiffs would have in trying to collect, and also where the case might go from here: The catch is the plaintiffs could start collecting, in theory, but Chevron doesn't have any assets in Ecuador. So the plaintiffs will have to go to other places around the world and say there's this judgment that you need to respect, and in theory they can try to repossess Chevron's assets in those countries.