[Potowmack]

However, if does this, he should be liable for criminal acts against people on his property.

In Virginia, at least, a property owner is almost never liable for criminal actions performed on his property by someone who is not in the employer's control.

[Little Ray]

Well if he prevents visitors from taking steps to protect themselves, then the landlord SHOULD be responsible. After all, it IS within his power to allow visitors to bring their weapons.