Hi Emily

On the bare facts, seems a nasty, petty and needlessly hurtful decision that says more about your directors than ever it does about the employee and reputationally may rebound upon them.

But, strictly legally, can't see why they can't do that, provided of course there's no unlawful discrimination etc involved,

In reply to David:

Seconded.

In reply to David:

The reason I believe they do not want to invite him is just because he is leaving a couple days later

As said above 'unless it's discriminatory, then yep, they don't have to invite him'. But you might just want to point out that it might look a bit mean-spirited and those that are still there might well remember that. 

They are still an employee until they leave so can’t see why they should be excluded in my view. Also need to be mindful if they felt they were being excluded due to a protected characteristic under the equality act 

Emil, I think folks below have it covered. I often say to bosses, just because you can (and it's legal) doesn't mean you should. Sounds like they are emotional about the leaving decision forgetting, perhaps that, people who stay notice these things and it leaves an impression which might not be exactly as the boss intends it to be.

What might be pragmatic, cost effective and expedient to them, could look immature, mean & anti values to others. Good luck. I appreciate challenging bosses often feels like a career ending conversation.