IIRC all of the past ones have worked over LAN, including over a private VPN if you so desire. I definitely played pirated copies of 1 and 2 with my mates. I had no real desire to get very deep into 3 because the campaign storyline was so stupid, but I don’t doubt you could.

It’s only online matchmaking with randos that you’ll be blocked from, which if you ask me is not really that much of a detriment.