If it's not part of the lease that the property is "non-smoking" - then I would inform the police officers that if they harass you once again based on the complaints of this neighbor you will be filing a lawsuit against them for harassment.
Law Enforcement Officers have the right and the duty to stop and question any citizen, whenever a felony has been committed and they have reasonable grounds to believe that the citizen may have been involved in that felony. If this should happen to you, your first reaction should be to cooperate fully with the officer. This is not harassment, unless the questions asked do not or cannot pertain to any real crime.
At your first opportunity, when you suspect that you are being harassed, you should ask, "Am I under arrest?" This forces the officer to inform you of your official status. If he or she does not formally arrest you at that point, then you are still a "private citizen" with all the civil rights thereof. You do not have to answer any questions, or allow the officer into any premises for which he or she does not have a warrant. Ask the officer, "What crime is under investigation?" The answer to this question should allow you to decide whether the officers questions are legitimate. Only then, if you are being harassed, should you use any of the following tactics.
You should not volunteer information about any persons or incidents, no matter what is promised to you. Anything you say can be used against you and others, and could be used out of context to mean something you had never intended. You will not clear yourself by naming others or describing events. It is best not to say a word until you have legal representation present.
Sometimes you could be subjected to bigotry, insult, or epithets from police who feel that intimidation will get them results from otherwise reticent subjects. Do not go into shock, do not lose your temper and do not respond in kind; it will only serve to pour more fuel on the fire and make matters worse. If you can remember exact words and details, write them down at the first opportunity and talk with a lawyer about whether you have adequate grounds for a civil rights complaint.
The police may take you to the station to talk. If this happens, ask to have an attorney present. Then, shut up. Don't say anything until the lawyer is there with you, and speak only if he advises it.
If you are in a public place with a multitude of neutral witnesses, like an event in a public park, you can speak a little more freely. Just remember, witnesses can work against you, too, so watch what you say and keep your temper.
If you are at another's home when the police come in, you should keep quiet also. Avoid incriminating your host. You really don't know what grounds are being used for the raid, and you probably don't know they are innocent of whatever it is; so avoid incriminating yourself or others. In this case, the time to act is afterwards; see an attorney.
In your own home, if the police ask permission to come in, the answer should be "NO." You should step outside and talk with them. If the weather is too inclement for that, or if they don't like this approach, offer to go to McDonald's or to the police station. You don't have to let them in without a warrant. If you are asked, "What do you have to hide?" turn it around and ask "What kind of question is that?" If they are not asking to come in, but breaking down your door, give way and let them in. Don't fight them or make any insults or threats, but remember all that is said and done, make notes, and get a lawyer.
If the officer looks frightened or angry, take extreme precautions not to do anything to startle him or make him think you are about to do him harm. This is a time of maximum risk to yourself, so be very polite and don't do anything that may be interpreted as a threat.
If the worst happens and you are injured during the course of an improper police action, go to the nearest Emergency Room for treatment. Even if the injury appears to be superficial, the hospital is required by law to notify the police in the case of an assault. This will begin the process of documentation for your eventual complaint or lawsuit. The hospital's report will be instrumental in substantiating such a complaint.
While the law recognizes many different circumstances under which the police may conduct a search of persons or property, only a few are relevant to this discussion. Of course, you are perfectly within your rights to ask the officer why he is searching you; his answer will help you to determine whether you have grounds for a complaint. (You always submit to the search; if the officer is acting improperly, you may file a complaint later.)
The Limited Protection Search is most easily used for harassment purposes. The law enforcement officer is permitted, if he has cause to suspect that a person is armed, to "frisk" that person for weapons. While this may be undignified, it is no more than that; if you are armed, surrender the weapon voluntarily before the search begins. This establishes that you are willing to cooperate with the officer, and limits the scope of further harassment. (Of course, if the weapon you carry is illegal, there are other consequences.) If you are not armed, it doesn't matter; even if he were to find contraband on your person, he probably could do no more than confiscate it, because it might not be admissible evidence.
If you are a female, you have the right to have a female witness present during the search. Another harassment tactic involves the "Plain View" search, which is not a search at all. This involves the officer's simply seeing some item which he defines as contraband; he has the right to confiscate it, as well as to take any further action as appropriate. Though this can be a major inconvenience, you can file a complaint against the officer through his department's Internal Affairs division, and you may be able to recover your property.
If you are actually arrested, then the officer may search your person and all of the surrounding area within your reach. This "Search Incident to Arrest" is permitted to insure that the arrested person cannot obtain a weapon or destroy evidence; any contraband or evidence relating to the reason for the arrest is admissible. You can do nothing about this, so relax. (It may be a tactic to rattle you. Don't let it.)
One special case: when the property to be searched is an automobile, the requirement for a search warrant is waived. The officer must still be able to prove to the Court that his search is "reasonable," but he does not have to obtain a warrant to make the search. This is because the vehicle is mobile, and could be gone by the time a warrant could be obtained.
Once again, we cannot make the warning strong enough: DO NOT resist a police officer or other law enforcement officer when he insists on making a search! Better to submit to the search than to the arrest or other consequences that could result from resistance! If you believe that the search was not reasonable, take notes as soon as you can. See an attorney. If you have a case, your attorney will deal with it.