Whether Hawaii considered Senior and SADO to be married is immaterial to whether the UK would consider the Hawaii marriage to be bigamous and thus invoke the illegitimacy clause of the 1948 BNA.
For Barry to be a UK subject and dual-citizen would depend on how the UK would apply their own 1948 BNA law and the Kenya Colonial 1902 Marriage Act.
Here is a comment I posted to Leo (which he has refused to publish) beginning with the Factcheck.org statement:
“As a Kenyan native, Barack Obama Sr. was a British subject whose citizenship status was governed by The British Nationality Act of 1948. That same act governed the status of Obama Sr.‘s children.”
Parsing this statement, I note the careful lawyerly reluctance to explicitly state that Obama II, like his father, was also a British subject at birth. The statement only says that the 1948 BNA "governed the status" of his father's children in general. IOW, the statement invites the reader to conclude that BHO II was a dual citizen British subject at birth, but does not say so.
If the 1948 BNA "governs the status" of Obama Sr.'s children, then any exclusions in that act must be considered. As you recently blogged:
“The State Department Has “Always” Recognized And Abided By Foreign Laws Concerning US Citizens Born With Dual Nationality.”
Therefore we must not be squeamish in applying the 1948 BNA to Obama II.
The 1948 BNA says that the act does NOT apply to illegitimate children:
“(2) Subject to the provisions of section twenty-three of this Act, any reference in this Act to a child shall be construed as a reference to a legitimate child; and the expressions “father”, “ancestor” and “descended” shall be construed accordingly.”
http://www.uniset.ca/naty/BNA1948.htm
My understanding is that a bigamous marriage is a nullity and the children of a bigamous marriage are illegitimate under the UK Legitimacy Act of 1926. BHO II himself has recognized his stepmother, Kezia, and her children as family and wrote in “Dreams” of his father’s shortcomings and doubts about the marital status of his parents.
In a Daily Mail story about Kezia, presumably based on information provided by her, BHO Sr is described as a “bigamist” and the presumably legal Kenyan tribal marriage between Obama Sr. and Kezia is described in some detail:
http://www.dailymail.co.uk/news/article-506338/Barack-Obamas-stepmother-living-Bracknell-reveals-close-bond---mother.html
In applying the 1948 BNA to determine whether a marriage is bigamous, it seems that UK authorities would look to the 1902 Kenya Marriage Act (KMA). From what I have found so far (not a lawyer) the 1902 KMA appears to have still been in effect in 1961 in Kenya Colony.
Under the 1902 KMA, tribal marriages are legal and subsequent marriages are bigamous, including even marriages following Muslim marriage:
37. Marriages under native law or custom.
“Any person who is married under this Act, or whose marriage is declared by this Act to be valid, shall be incapable during the continuance of such marriage of contracting a valid marriage under any native law or custom, but, save as aforesaid, nothing in this Act contained shall affect the validity of any marriage contracted under or in accordance with any native law or custom, or in any manner apply to marriages so contracted.”
“49. Contracting marriage under this Act when already married by native law or custom.
Whoever contracts a marriage under this Act, being at the time married in accordance with native law or custom or in accordance with Mohammedan law to any person other than the person with whom such marriage is contracted, shall be guilty of an offence and liable to imprisonment for a term not exceeding five years.”
http://www.kenyalaw.org/kenyalaw/klr_app/frames.php
Enquiring minds want to know.