diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 40ca9d7..e9abd9e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -4,3 +4,5 @@ To improve this page, head to <https://github.com/adr/adr.github.io>, edit `_pos
 
 See [Chirpy's Text and Typography](https://chirpy.cotes.page/posts/text-and-typography/) post for information on possible styling.
 The [source](https://github.com/cotes2020/jekyll-theme-chirpy/blob/master/_posts/2019-08-08-text-and-typography.md?plain=1) shows the respective Markdown source.
+
+We expect contributors to submit original material only that does not conflict with the [license](LICENSE). We also request them to respect the [ACM Code of Ethics and Professional Conduct](https://www.acm.org/code-of-ethics) in their contributions and communication about them.