In the Hippias Minor, Socrates raises the question whether liars have the power to do something or nothing (365d). In general, cases such as telling a lie raise the question whether agents have the power to do actions that are wrong, incorrect, or otherwise such that a good person would not want to do.
In the course of the dialogue, Socrates leads Hippias to agree to a number of controversial claims, all of which involve the thought that having the power to do x, even when x is a mistake of some sort, requires having the same knowledge that enables the agent not to make that ‘mistake’. This conclusion is compatible with the Socratic view that no one does wrong willingly: if it’s the same person, the good man, who has the power to do right and to do wrong, his power to do wrong could hardly ever be exercised because he would never want to do wrong. But, perhaps surprisingly, in the Hippias Minor Socrates does not push the idea that no one wants to do what is bad, but rather the point that nobody would want to be in the condition of being unable to do what one wants (374a-c). In the end, the Hippias Minor suggests that an agent might want - and have the power to do - something wrong, and yet that this is not a power worth having.