My argument is that although robots.txt is a machine-readable way of asserting reservation of use, it's not the only machine-readable way, and the law does not

My argument is that although robots.txt is a machine-readable way of asserting reservation of use, it's not the only machine-readable way, and the law does not seem to place a burden on the rights-holder to choose a particular 'machine-readable format'. While a court would likely conclude that a watermark on an image is not 'machine-readable' (I say likely—OCR technology would however make it possible that a court could find that a watermark is machine readable), I would say that because the law does not require a specific method, I think it might be found that a copyright notice in the footer, or in an image caption, is indeed 'machine-readable'. On balance, I agree that there's a lot of things we are woefully underprepared for coming up in the very near future on using tools in this way to generate art. The answer is not simply to try and lock up all the art away from the robots—but I don't know what the answer actually is.