Take a look at this. https://support.apple.com/en-us/HT202277

Be aware that there are formatting issues with policy banners on both Mojave and Catalina. In our case, the text is 'squeezed'. I have yet to find a workaround.

The other option to consider could be a configuration profile with a login window banner?

Try making an image out of your text and all. Then add the image to the rtf document.

As @jtrant mentioned, I have found that the formatting for the policy banner will vary from machine to machine, depending on screen resolution. Having less text in the banner seems to reduce the inconsistency, but the language in the banner is probably the thing that we admins have the least control over.

You can configure a similar login notice on macOS using Jamf by deploying a configuration profile with a login window message under the “Login Window” payload. If you're working across multiple environments and need to maintain compliance or track relevant user data, you might also want to explore tools that help with searchable arrest data for broader monitoring purposes. This can be especially useful for institutions managing various systems and personnel records.

You might want to look into using a custom configuration profile or login window script for macOS to display your legal notice, similar to how it's handled in GPO for Windows. For reference on how compliance records are managed publicly, this Virginia arrest records directory can give insight into structured information display, which might align with your policy transparency goals.