Great topic!
I will create a link for the contract I use later...like Yukidomari said though, it is expensive to enforce, at best. I think best practice here is to maintain a good - or even just tolerant and diplomatic relationship - with owners of puppies, and involve them with the "breed network" of their country - even if it is not a formal club. I think this is easier (maybe for a smaller breeder). I speak with the owners of my first litter weekly, usually through email or facebook - but, in my first litter I sold only 3 puppies, so three owners isn't too many people to talk to.
I think the biggest three problems presented to a breeder are:
1. The owner decides they can no longer care for the dog
2. The owner decides they want to breed the dog.
3. The owner fails to provide good care for the dog (this is probably the most difficult problem to detect).
For the first problem, if the breeder still has a good relationship with the owner, and if they have planned in case something goes wrong, and if it is written in the contract, it really should be no problem for the owner to return the dog. In my contract, I write that it is the owner's financial responsibility to return the dog to me (they get no refund, unless the dog has a genetic health problem). In reality, I know there could be problems for the owner to return the dog at their cost - so I make sure I have the money or other plans to arrange for a "return" ticket, if necessary. I will not ship a dog unless the person has visited my kennel before. I won't sell more than one puppy from a litter to a new owner (if it's a good owner, a puppy from a future litter is no problem), in case they have problems with the dog, but also because I believe it is best to only have one puppy at a time for socialization.
For the second problem, there is a program in AKC called "limited registration". With this program, the breeder sells a puppy with no breeding or conformation showing rights - litters originating from the puppy cannot be registered. The dogs can participate in obedience and other performance events (but I think they might have to be spayed/neutered to do so...). This registration can be cancelled, I think, if the breeder chooses to do so in the future, and be replaced by full registration breeding rights to the new owner. There is also the possibility of co-ownership - my signature would be required before a litter could be registered from a dog I sell. This can be permanent, or, like I plan to do with future litters, changed to "sole ownership" (new owner has all breeding rights, my signature is no longer needed) once the dog has passed minimum requirements (for me, it is HD, ED, DM, DNA registration, 1st eye test, temperament test - Canine Good Citizen, and also I want to evaluate the dog to make sure it has no disqualifying faults - eventually, I hope we will have a bonitation process here, but for now...). In maintaining a good relationship, I REALLY hope future owners will keep a dialogue with me about their breeding plans for "my dog", so I can share my knowledge and concerns. If the new owner doesn't like these options...they can find another breeder.
I don't know if there is a way to do this between AKC and FCI countries.
The third problem is very tricky, especially if the dog is living many kilometers away. Different owners have different ideas about what is a "nice life" for a dog. The laws in the US provide some VERY basic requirements for what is okay (dog must have clean water, not live on a chain, have food, medical care and clean facilities and shelter from the weather, and in most places, not be allowed to run free). The contract can (should!!!) require more, but if it is beyond what humane law requires, it becomes the obligation of the breeder to enforce. Humane laws tend to be very poor in enforcement and consequences, especially with a bad economy.
In some cases, breeders have been contacted by people who know the new owner saying conditions are bad for the dog, and the breeder can intervene. Again, this is where a relationship is very important with the new owner - if they are happy, usually they share stories, questions, photos, problems, successes periodically with the breeder (as long as the breeder responds in a nice way...). It could become a big problem, I guess if the new owner lost contact...