congress does not establish ground rules for square pegs and brunner williams on hold in these situations an agency cannot make around whole square by rewriting unambiguous statutory language. >> a take it be an ambiguous language you are talking to our references to 20250 and seems to me that is an odd kind of turned to drive such an important statutory interpretation question because what those numbers were all about is that they were supposed to separate major animators from minor in matters. they were supposed to be about the size of the facility. they were not supposed to hav have -- they were not supposed to make distinctions as to the type of pollutant. you are essentially using those numbers to make distinctions as to the type of pollutant rather than it seems to be a more sensible approach would be to say look at 250 and 100 numbers don't work for this new kind of pollutant. we are going to up the numbers and that will leave the rest of the statute in all the purposes of congress and cap. >> justice kagan recently think specifically for bid epa to do what your honor is describing