Under English Common Law, still the law in almost all English Speaking Nations (including all of the US States and Canadian Provinces with the exception of Louisiana and Quebec, and then only in parts in those two Civil Law Jurisdictions) when a person "Rents" real property from another, the "Renter" is the OWNER of the property for a time period (Which can be month to month, year to year, or any other time period agreed by the parties, but if nothing is agreed then, in most areas, the law presumes month to month leases).
Thus a Leaseholder (The correct legal name for a "Tenant" or "Renter") has all of the right the landlord had to the property when the Leaseholder leased the property from the Landlord. Now the Landlord can retain property rights to the leased rental unit, but unless retained, all rights to use the property belongs to the Leaseholder NOT the Landlord. For example if the Leaseholder tells the landlord NOT to come on to the lease property and the landlord does enter, that is trespassing UNLESS the Landlord can show he retained the right to enter the Leasehold (i.e. the lease setting up the leasehold contains a clause the landlord can enter the leasehold for inspection/repairs etc).
Notice the law, it is up to the landlord to show he retain whatever rights he retained to the leasehold. The law presumes the Leaseholder holds ALL possessionary interest in the property. The only obligation the Common Law imposed on a Leaseholder was to require the Leaseholder to make every effort to preserve the leased property for the landlord whenever the lease expires (i.e. No damage to the leasehold caused by the Leaseholder or anyone under control of the leaseholder including third parties who do damage that the Leaseholder is in the best position to prevent).
Now Leaseholders are NOT responsible for "Wear and Tear" to the leasehold, but what is "Wear and Tear" and what is "Damages" are often up to a Judge and Jury to determine. A third party shoots the door out, is generally called "Damages" and the Leaseholder has to pay for the repair, but if the door falls apart do to age (or previous damages done before the Leaseholder moved into the unit) the landlord must pay for the repairs as the result of "Wear and Tear". This dispute should be resolved by insurance companies and I recommend Leaseholders to obtain Rental Insurance, more so that the Insurance Companies can argue who is to pay for the damages then anything else.
AS to weapons (and pets) the law in both the US and Canada are clear, unless there is a State or Federal Statute to the Contrary the landlord can impose a ban on both for any reason or no reason.
There have been a push to end bans on pets and such bans of pets are NOT permitted in Public Housing by Federal Law since the 1990s when studies were presented to Congress that having a pet helped the elderly live longer and the reason elderly people in public housing did not have pets was do to pet bans. Thus Congress made such bans illegal as to Handicap and Elderly Public Housing the then a few years later to all Public Housing. The expansion to ALL Public Housing was called for when many elderly were complaining of NOT being able to have a pet for they were in regular Public Housing not elderly public housing and could NOT get into Elderly Public Housing for the local Housing Authority determined they could do well in their existing apartments and there was no need for them to be moved into Elderly Public Housing (Regular Public housing and Public Housing for the Elderly and handicap are two aspects of the Public Housing laws in the US, in many ways the same laws apply to both, but if a housing project was intended for elderly and/or handicap a different set of law and regulations apply, thus two different changes in the law was required).
Now the main reason the act passed was, first the Elderly campaign for it but the larger the studies on pets and tenants were ridiculous. Second, 95% of all landlords banned pets, yet 1/3 of all Leaseholders reported in surveys on having pets. These two sets of data should not occur, but were (and still are). I once ran across a Pro-landlord web site that pointed this out and stated that Landlords were setting themselves up for losses by requiring a pet ban when it is almost impossible to enforce such a ban (Warner brothers had a Cartoon staring Tweety bird in such a situation, Tweety's owner had to hide her from the building's detective enforcing a "No Pets" ruled while Sylvester was trying to make Tweety a mid day snack, at the end of the Cartoon the Detective went onto the intercom and demanded that he new a tenant had a pet and that the tenant who had that pet had to get that pet out of the building right now, all you saw next was a huge number of pets running over the detective, if I remember right including an elephant and a monkey, but I mention that Cartoon to show that the banning of pets and that tenants having pets dispute that ban has a long history).
Twenty Bird and Sylvester in "Room and Bird":
http://www.imdb.com/title/tt0043979/Actual Cartoon:
http://www.jogyjogy.com/watch.php?id=19db3I bring up pets for the existence of pets is a lot easier to determine then if the leaseholder has a weapon. Unless the landlord sees the pet or a Weapon (and prove that such pet or weapon is in the control of the leaseholder) the landlord has no right to end the lease early. If the landlord does have the evidence the landlord can end the leasehold as a fundamental breach of the term of the lease (Unless such grounds are NOT permitted by law, racial discrimination is an example of illegal grounds, but pets and weapons bans, unless illegal by statue passed by the Federal Congress, a State Legislature or local Government are NOT illegal. The only example of such bans is the Federal Ban on Prohibitions of pets and then only to public housing).
As I mentioned earlier the pro-landlord web site commented that any landlord that banned pets was heading for trouble given the sheer number of tenants who have pets and will have pets and will LIE about having pets to get into a rental unit. The Web site advocated that pets be permitted subject to inspection and approval of the pet by the landlord AND an addition security deposit to cover possible damages done by the pet. In my home state the Statute governing Security deposits limits such deposits to the equivalent of one month's rent, but the Courts have permitted landlords to require additional security deposit if it is a pet deposit as opposed to normal security deposit for the leasehold. This is the better way for Landlords to protect themselves from damages to pets instead of a blanket ban on pets.
I bring up pets for it is a clear example of landlords setting terms they can NOT enforce AND that leaseholders know it and thus violate it on a frequent basis. The better solution is to permit pets with approval AND additional security NOT a simple ban on pets. This is even worse with a weapon's ban, how can you find out if a leaseholder has a weapon WITHOUT trespassing? The Courts will interpret any lease clause that permits you to enter the leasehold narrowly, i.e. you can only do so to do the acts you claim, and then only at times and dates that are reasonable. Remember when you leased out the property possessionary interest was transferred to the Leasehold/Tenant/Renter and any right the landlord retained can not interfere with that right to any excessive degree.
If the lease says you can inspect, your inspection must be limited either by your actions (how often your do it) or by the terms of the lease (Which can NOT be so liberal that you can enter the leasehold at any time, some restriction as to entrance has to exist). Furthermore your inspection must be limited to what your need to make sure the landlord is NOT suffering from any hidden loss NOT to look over every inch to see if the Leaseholder is following all parts of the lease (i.e. you can NOT search the dressers to see of the tenant had a weapon that you ban in your lease UNLESS you can show HOW the mere existence of such a weapon will lead to you having a financial harm AND that you needed to look in the dresser to make sure YOU, as the landlord, was NOT suffering nothing any harm. Notice the burden is on the LANDLORD to prove this NOT the Tenant/leaseholder). Furthermore if the court rules that your exercise of the clause to permit you to enter the leasehold was excessive the landlord is guilty of trespassing. To prove trespassing all the tenant has to show is the landlord entered the leasehold without permission of the tenant. It is up to the landlord to show he had permission to enter the Leasehold either by permission of the tenant or a lease provision that permitted landlord to enter. Furthermore the burden is on the landlord to show the entrance complied with any such provision, if the landlord can not show such compliance the landlord had committed trespassing. My advice is avoid the whole situation and kept any such inspections limited to make sure no damages is being done to the leasehold NOT to look for pets, drugs, weapons or any thing else banned in the lease.
Just a comment on bans in leases, any ban in a lease should be limited to what the landlord can prove by visual inspection of the rental unit from the outside or during any reason inspection. Any other ban is simply NOT enforceable, Landlord can ban weapons, pets, drugs, etc., but unless the landlord has EVIDENCE that such ban has been violated by the Tenant there is nothing the landlord can do. Such bans are a waste of time and ink and more often then not used as excuses to end a leasehold when the landlord wants it ended for other reasons. The Court know this and dislike kicking out any Tenant except if the term of the lease has ended, rent has not been paid, or it is clear actual damages have been done and the only way to prevent further damage is to kick out the Tenant. The first two are easy to prove what most landlord use, the last one is hard to prove and best avoided.