the neighbor is placing rat poison outside under her car?

"I'm afraid that she is going to poison my dog"

Since you say you keep your dog on leash, then he can't get to the poison under HER car. The police have said she has a right to do that.

Has she actually had rats in/around her car? If so, the only other option would be to ask her if you can pay for a pest control company to come out and professionally remove the rats (trap them). Note, however, that a child or dog could get fingers/paws broken by a trap strong enough to kill a rat....

BTW, rats can carry horrible diseases: http://www.cdc.gov/rodents/diseases/direct.html . If there is even one lurking about, believe me, you want it dead.

Rats actually carry relatively few diseases (no more than most any wildlife) and generally you need direct contact to catch it from an infected rat (and being infected at all is pretty rare in an urban setting). They're actually very "clean" animals. Not to say they can't pose a health risk - but so can any animal (humans included).

If it's in public space (or anywhere the public/wildlife might be), as someone else mentioned, most places have ordinances requiring it to be in enclosed containers to prevent other wildlife/pets getting to it. That's the best course of action... however, you're counting on law enforcement to actually know laws (oddly rare).

Frankly, I'd just move it and smash it against her windshield. Do it enough times and she'll get the hint (feign ignorance, of course). Failing the spite to do that, ask her to put it in an enclosure to prevent other animals from getting to it.

It's likely not a threat to you dog if he's on a leash (he'd have to get under her car and eat it) - but it might be a threat to other wildlife. And regardless, I don't see the point in putting it under one's car... in her own apartment, maybe. Rats, being prey for many other animals, instinctively tend to stick to walls/stay away from being out in the open - so if the goal really is to get them, putting it against walls of the building would make a lot more sense.

Why is your dog out without being on a leash?

None. There is no legal action you can take. You can remove the rat poison.

Why is your dog roaming around with no leash? There is no legal action you can take since its not illegal to put out rat poison for rats.

Most cities have ordinances that require rodent poison placed in public areas be in special containers which allow rodents to access the poison but not pets or larger wildlife. Check with your local health department.

Take a broom and dust pan out every so often and get rid of that crud. Its a danger to every animal (and CHILD) out there. If it doesn't get your dog, it might get someone else's cat.

Side note: I'd probably put the mothballs and poison in a plastic bag and keep it where your dog can NOT get to it. If she keeps putting it out, you keep bagging it. Once you get a gallon bag full take it to your landlord and give him the bag. (Take a picture of his look holding the sack). If he wont do anything after that print out that photo in color, go door to door in your building, and get people to sign a petition that they want to ban poison from being placed by residents.