OP said the yahoo software is following links within the email content to an outside server -- that server can control access. Even if that software doesn't respect robots.txt, which im assuming it does, the server should still be able to see what/who accessed the link, and if it truly is coming from yahoo, then blacklist it.
The court is blaming yahoo for their security shortcomings.
in the least, the urls should be protected if they are private access, unique pin per url, simple login account, named access, etc.
I find it more unethical that a court will charge a lawyer per link hit for information that costs them absolutely zilch to host than a free email service selling targeted advertising based on an algorithm it uses when scanning the emails...
pro tip of the day: don't hire a lawyer who uses free yahoo email and doesn't click the opt-out button.