if sue loves joan thomas joe sue can marry him and tom cannot. the difference is based upon the different sex. why is that not a straightforward question of sexual discrimination? >> to reasons, all of these courts have involved in treating classes of men and women differently which is now we have here. even more fundamentally than that the court has recognized that it is appropriate to draw lines based upon sex difference related to biology and endorsement for a minute that it really is important and you will recall that is the case we had a law by determining citizenship of children born to the voiced or unmarried individuals overseas. the law said if it was the child of the citizens mother they automatically have citizenship. if it was the father and the father had to prove paternity and make child support payments up to age 18 which is an obvious sex discrimination. >> we know who the mother is. claiming to be the father. we cannot be sure. clicks that was the justification for the proof of parenthood. i would like to quote from the child sup