Forbid LLM contributions

CONTRIBUTING.md

@@ -51,6 +51,17 @@ one above, the
 [Install the Dart SDK]: https://www.dartlang.org/install
 [Install Node.js]: https://nodejs.org/en/download/
 
+## Large Language Models
+
+Do not submit any code written or modified by large language models or
+"artificial intelligence" such as GitHub Copilot to this project. These tools
+produce code that looks plausible, which means that not only is it likely to
+contain bugs those bugs are likely to be difficult to notice on review. In
+addition, because these models were trained indiscriminately and
+non-consensually on open-source code with a variety of licenses, it's not
+obvious that we have the moral or legal right to redistribute code they
+generate.
+
 ## Writing Code
 
 Dart Sass follows the standard [Dart style guide][] wherever possible, including