
So you are trying to prevent the owners of the dead dog from using the semen?
Your mother never kept a signed copy of a contract telling them of the endorsement.
Kennel club rules are that there must be a signed statement about the endorsements signed by buyer from the seller that placed them (your Mother In Law), if such statement cannot be produced by you, then yes the kennel club will lift the endorsements.
You need to check in the dog records for this statement, if she didn't do one then she did not endorse the dog properly.
https://www.thekennelclub.org.uk/media/8269/endorsements.pdf"Problems can arise when the new owner makes a request to the person(s) who placed the endorsement for this to be done, only to be told that they have no intention of doing so. This is an area where disputes can arise particularly with purchasers claiming they were not aware that the newly purchased dog would be subject to certain restrictions.
The parties concerned are expected to try and resolve the matter amicably between themselves. However, if an agreement regarding the removal cannot be reached, the Kennel Club is often asked to intervene in what can sometimes be a very difficult situation, especially when there are conflicting views on whether the breeder advised the purchaser of an endorsement at the time of sale.
The Kennel Club cannot comment upon the contents of a private contract especially relating to whether any terms described therein have been met or not, but can only look at whether the endorsement has been placed in accordance with our Rules and Regulations.
In order to comply with the Kennel Club rules on placing endorsements, the KC requires that the dog be in the physical possession of the endorser and that they obtain a written agreement, ideally in the form of a private contract, signed by the new owner to acknowledge that they have been informed that an endorsement has been placed. If endorsements are being used, it is helpful to both parties if the contract mentions why these have been placed and under what conditions they would be removed (if at all).
This contract must be signed and dated by the purchaser showing that they have been informed of the endorsement prior to or at the date of sale. Even if the breeder chooses not to draw up a full contract, there must still be a document stating which endorsements have been placed, signed by the purchaser
If the new owner believes that the endorsement(s) has not been placed in accordance with our rules and regulations, and they are unable to reach an agreement regarding the removal with the person who placed them, the owner of the dog can apply in writing to the Kennel Club to request the removal of the endorsement."