Thankfully, I don't have to bother explaining to all my law-and-politics professor brethren (and sistren, Profesora) exactly how Fish is being misleading, because Jeff Goldstein over at Protein Wisdom took care of it. Jim Lindgren over at Volokh, on the other hand, seems to have been completely taken in -- which is not surprising, since Fish is being a bit too precious in his English department rhetorical trickiness.
In case you don't get all the "Inside English" references (like New Criticism, etc.), just know this: Stanley Fish is most famous for writing a book called, Is there a Text in this Class?, to which his answer (grossly simplified) is "No." So, when he writes writes of the Constitution that "the Constitution can't mean what the text alone says because there is no text alone" and "Intention comes first; language, and with it the possibility of meaning, second. And this means that there can be no "textualist" method, because there is no object - no text without writerly intention - to which would-be textualists could be faithful," what he is getting at is that as a text the Constitution doesn't really exist. Though on the surface it appears he is offering a rather conservative approach, it is actually a Trojan Horse to get readers to say, "Gosh, there really is no Constitution, only intention. And since we only know of the framers' intentions through other (non-existent) texts, we are really the ones who determine their intention." So, the distinction between what we want the Constitution to mean and what it actually means is moot -- we simply say that the framers wanted to to mean what we want it to mean, because all of our "reasons and evidence publicly offered" are textual as well.
All this is a rather old and tiresome slipperiness to which folks in English departments are accustomed; Fish is counting on NYTimes readers and my law-and-politics siblings not to get it.