Testing for Equine Diseases and Ownership of a Test Mare

Interesting fact: apparently Iceland prohibits importation of foreign horses, or the return of exported horses

I read this story yesterday (which I found on the blog If Wishes Were Horses, always an interesting read!); there is a text and video story about a particular mare.  
In quick summary, according to the article, when non-U.S. stallions are brought to the country they are tested for Sexually Transmitted Diseases (STDs) by being bred to healthy mares.  The mares conceive, the embryo is deliberately aborted, and if the mare contracts the disease then it is known that the stallion is infected and it cannot be used for U.S. breeding.
One of these "test mares" was discarded from the testing center and was bound for slaughter; a rescue organization saved her from a kill pen, and through the organization's facebook page, the original owner identified her mare (6 years later) and the two were reunited!

The story gave rise to a number of legal implications, the two I want to address in following blog posts are:
1. While in this case it is a rescue who purchased the mare, if it were a private party, would you have to give the horse back to the original owner?
2. The legality of the method of testing

Do you have any particular insights (or questions) into either of these issues?