“We live in a multiple dwelling of 70+ apartments. The landlord posted a notice on the main doors for a few days, that anyone caught letting in others that do not live here will be evicted. This was never added to any lease. My husband came in with another tenant and another man who, we thought, still lived here. At the time we did not know that this other man no longer lived here anymore. Now the landlord wants to evict us for letting this man in. Can he do this? As I said, this notice was never added to the lease.”
Can your landlord change the terms of a lease by posting a notice in the hallway? The answer to that is probably no: A lease is a contract, and unless stated in the contract to the contrary, one party cannot change the terms of the contract without the other party’s consent.
That doesn’t answer your question, however. There may be terms in your lease that could be interpreted to include this kind of behaviour. Just for example, if your lease says you may not cause a nuisance to other tenants, your landlord could argue that letting non-residents into the building constitutes a nuisance.
Also, your local law will govern to some extent what your landlord can and cannot do in terms of changing lease terms, and what the proper procedure is to go about doing that. This is particularly true if you live in a rent-controlled area.
Finally, there is the procedural angle. In some places, a landlord must file a lawsuit in order to evict a tenant; in others, the burden is on the tenant to file suit in order to stop an eviction. Depending on which type of jurisdiction you live in, it will be harder or easier for your landlord to proceed.
The first line of defense here would be to talk to the landlord and/or manager and try to smooth things over. Failing that, you should consult an attorney immediately and be prepared to take whatever action you decide is appropriate.