The two of them could have been legally married in the Coast Province of British East Africa IF Stanley Ann became a Muslim and agreed to it, because in that province, Britain had signed an agreement with the ruler of Madagascar to permit Muslims to be governed by sharia law. So up to four wives were legal.
But IF they claimed to have married in Hawaii, that marriage would have been null and void, because bigamous marriages are not permitted in the U.S. (yet).
As yet, NO MARRIAGE CERTIFICATE HAS BEEN FOUND.
It is possible, in fact, that Obama senior pretended to be married to Stanley Dunham in order to persuade Immigration and Customs to extend his student visa.
So, all this story does is render the whole business even more suspicious.