I am not an attorney. I do not play one on TV either.
The following is NOT legal advise.
Was your offer FULL PRICE and without a single contingency?
if yes..maybe you can huff and puff with an attorney but you won't prevail.
Without the presence of a executed contract with consideration, the buyer and seller did not reach an agreement. No contract therefore exists.
Be aware, the seller is not required to provide any explanation for their action. They can simply say "Neyet," and that is all that is needed. Even 'Neyet' is not required. You offer can be ignored.
Now, the other side of the question that seller ask is, "Why is the buyer allowed to escape their buying commitment for any reason at the buyers sole desecration?" Would you not deem it only fair that the seller have some 'sole discretion' to apply also?.
In real estate transactions the BUYER has 100 times more protection than the seller.This seller made a prudent decision BEFORE they become obligated.
You could have regrouped and created a 'Make me move!" offer.
You didn't. So, the seller will stay put.