Just a few clarifications to the translations, in case it confuses some readers:
"What if someone... to gain some advantage" => To be more accurate, it actually says that the Duchess's worry is that the Royal Family will be complacent to the Sperados' actions if they learn that Leslie's sacrifice is necessary for Sperado's power.
"finding out about the law" => "finding a loophole in the law"
Basically, they created the law with the assumption that the parents will always act in the best interest of their children. Which is why it prompted their conversation about revising the law.