User blog comment:It's Good to be the Queen/Get over yourself, Morgana/@comment-5674726-20121028214949

"I would really like to know what makes Morgana think she has any right to the throne of Camelot. She is the result of an adulterous affair between King Uther Pendragon and his best friend's wife. (Some friend.) As the illegitimate issue of a monarch she is not in the line of succession; ineligible to inherit the throne."

What interests me is not that Morgana believes that she has a right to the throne but that Gaius does. Unlike Morgana, Morgause, Agravaine, etc, Gaius has no motive to see Morgana on the throne so, if he believes that she has a claim on the strength of her royal blood, it's very possible that the Camelot succession laws aren't as hard and fast as in modern monarchies.

An illegitimate daughter could have some rights of inheritance under Camelot's laws, even if few would support her claim ahead of that of a legitimate son.

Morgana is one of two living people (that we know of) with Pendragon blood.

Until/unless Arthur fathers an heir of his own, his death means a succession crisis that could allow Morgana to claim the throne on the strength of her royal blood.