Rules and Regulations - does it contradicts a a lease?

[Mary Jay]

Hi guys, sorry if I am asking a silly question. Its my first time I inherited tenants with a purchase so I am a bit lost...

All my other rentals Ive bought with no tenants...

Anyway, 

1) if I send the tenants my rules and regulations, would it sort of contradict a lease agreement?  Because a tenant in the court can always say : this or that was not in the lease so I never agreed to your rules and regulations.

2) And whats do you usually put into your rules and regulations? 

Thank you!