This is Google were talking about. We're probably going to find out that you can remove the mark by resizing or reducing the color depth or something stupid like that. Remember how YouTube added ContentID and it would flag innocent users while giving actual pirates a pass? As said in a related article:

"There are few or no watermarks that have proven robust over time," said Ben Zhao, professor at the University of Chicago studying AI authentication. "An attacker seeking to promote deepfake imagery as real, or discredit a real photo as fake, will have a lot to gain, and will not stop at cropping, or lossy compression or changing colors."

https://www.maginative.com/article/google-deepmind-launches-new-tool-to-label-ai-generated-images/