Because employees are not their employers, and have a life outside of work in which they still do stuff? Seriously. Yes, it is draconian.
Besides, if the law firm really wanted someone in there for hand-wavy reasons, why would they not just hire someone for it? Blacklisting is petty, counter-productive, trivial to abuse, and solves nothing.
So what? There are a lot of laws and policies based upon where you work that restrict you in your personal life. The lawyers can get over it. This is a non-issue, and I suspect the law firm did all this on purpose to drum up another lawsuit against MSG.
Besides, if the law firm really wanted someone in there for hand-wavy reasons, why would they not just hire someone for it? Blacklisting is petty, counter-productive, trivial to abuse, and solves nothing.