[quote="WhiteFang"][quote="TheLionPrince"]Scar was an unrightful king, but he can still pick and choose any lion to be his successor just as any righful monarch of the Pridelands can. Therefore, Kovu does a legitimate right to the throne.[/quote]
I don't think Kovu had any legitimate to the throne. Because he was not chosen by a king of Pridelands. I mean, Scar was seemingly the king but not really in legal matters, so his choice did not give anyone any real rights when it came down to the true kingdom.
I don't think it was an option for her. She was the only blood heir of the king and the only person trained to rule, so she'd had to take the crown whether she liked it or not. But if it came down to her threatning to leave if they tried to make her, I believe Simba would've trained Kovu into a ruler and given the crown to him if Kovu wanted it. As Simba apparently came to trust Kovu and think well of him, and Kovu was to be a king anyway thtough marriage to Kiara. Simba would try to solve the problem with as little risk and trouble as possible, and this way the only thing that would change is which one of the anyway intented couple holds the crown/is the law.[/quote]
Pretty smart answer, WhiteFang. However, I disagree with you on Kovu's legitimacy to the throne of Pride Rock. In
The Lion King II, it is mentioned many times that he is Scar's heir, and when Zira told Simba that Kovu was hand-chosen by Scar to become king, Simba took that very seriously. Enough to growl at him which made poor Kovu

knowing he is a rival to him. So, if it is taken seriously that Kovu is Scar's heir and has a legitimate right to the throne, then, Kovu is a legitimate heir. On top of that, Scar is of royal blood, and when Mufasa died and Simba disappeared, the pride had no choice but to accept Scar as their king (until Simba arrived) so Kovu had a right to the throne only through Scar.
Also, Kiara doesn't have to take the throne if she doesn't want to. If the kingdom in The
Lion King movie universe is the same as kingdoms in our world, then, take into consideration that Edward VIII of the United Kingdom chose something similiar such as to abdicate from the throne when he wanted to marry an American socialite, which British officials wouldn't allow.
Even if she is threatened to leave the throne, true, Simba could train Kovu to become King, but if he wants to leave with Kiara and has no interest in the throne, then, Vitani would have the right only through Kovu alone since a sibling of a royal heir are entitled to the throne. If she doesn't want the throne, the Pridelands is pretty much screwed.