by the United States government, United States Code — Title 42, Chapter 85…
“ The term “lowest achievable emission rate” means for any source, that rate of emissions which reflects— (A) the most stringent emission limitation which is contained in the implementation plan of any State for such class or category of source, unless the owner or operator of the proposed source demonstrates that such limitations are not achievable, or (B) the most stringent emission limitation which is achieved in practice by such class or category of source, whichever is more stringent. ”
