Do i need to implement Security for my webpage, if it is only connected to a LAN

I am making a websocket server that can communicate with clients.

This server is going to be on a private vLAN channel on a public place, AKA only the staff have access to the network which the server is on.

When this is the case, do i need to implement SSL or any other form of security, if the “hackers” cant get access without being connected to the vLAN?