Why wouldn’t the marriage be legal?
Probably because of BHO Sr.'s polygamy problem.
Obama Senior was already married.
You didn’t know that bigamy is against the law in all 50 states of this country?
Therefore, even IF BHO Sr. and SAD contrived to get a marriage license from Maui County (for which there is no evidence), they were not able to contract a legal marriage under the laws of Hawaii or the United States.
There are many facts about this matter that will never be known, because all the persons who knew them are dead.
But it is beyond dispute that BHO Sr. and SAD were never married to each other.