Rules that are not legally enforceable arent worth the paper they're written on or not written on. Tenants have a wide variety of rights in their homes that rival what home owners enjoy. The question being common areas. Rule or no rule my guess is their prohibition of dispayed firearms in common areas is not legally enforceable. Having been a landlord for quite some time, and never again, I got to see how most of what I put on paper was just me straining my hand typing stuff.
I have been a landlord too. Can't say I liked it much. Threads like this remind me why I sold and moved on........