The limitations based on consanguinity derive from a policy of practical eugenics and reflect the increased possibility that such marriages will produce children with a genetic defect due to the limitations on their combined gene pool. The limitations based on affinity, by contrast, are predominantly legal and social in origin. The rules relating to affinity reflect the need to minimise the prospects of familial jealousies and dysfunction by preventing the intermarriage of people already related by marriage. Difficult questions arise on whether an adopted child may marry his or her adoptive parents, or the natural children of the adoptive parents. No matter what legislative decisions are taken, there will always be citizens who wish to evade the application of the law. There will be no problem if they relocate and establish a matrimonial home in a state that allows their marriage. But any attempt to evade such laws by going through a ceremony in a state that permits the marriage and then returning to the original state (which will usually be their state of domicile, nationality or habitual residence) will fail, and may even expose the couple to the risk of prosecution for incest or an equivalent offense.