Do you think a law of succession would have prevented the Battle of Hastings? Why?

But I am confused because the battle of hastings was because King Edward died childless, and the right to the English throne was in question. So an English assembly chose Edward’s brother-in-law, Harold, as King. But Edwards cousin who was the Duke of Normandy, thought that he deserved it. So him and his infantry invaded England and that was the Battle of Hastings..I thought that WAS the law of succession, but the question isnt making sense! HELP!! the book is Across the Centuries if anyones wondering