My work uses mifare cards if I recall it correctly. Using a simple nfc emulator app on a rooted phone, I could just clone the card instantly and use my phone to enter anywhere the card could.
This had obvious big security repercussions. Someone with bad intentions could just walk past you and copy the card. So they added personalized pin codes to all cards, every poor sod in the company now has to touch their badge + give in a pincode for you pretty much all doors. They are currently in the progress of renewing the entire security system to upgrade the security of the cards. (at great cost :))
So depending on the type of card used, it might be possible. I've tried it with many different security cards, it only worked with the one from my company. So it really depends on the type of card used.
https://play.google.com/store/apps/details?id=com.wakdev.wdnfc
I think it was this app, but I'm not 100% positive. Haven't rooted my new phone due to other security reasons, so I haven't tinkered with it lately.
Way to misunderstand federation + legal issues... Go cry foul on reddit, they share your "outrage" mindset
Just make an account on another server that is federated with them.