Legal question.

Ignoring the distressing and emotional aspects of the Shannon Matthews case, I would really be interested to know whether her mother was in fact charged with kidnapping her (rather than conspiracy to, or aiding and abetting kidnap). Because it seems to me at least arguable that a custodial or jointly custodial parent cannot in law kidnap their own child. As a parent you have the right to ground your child and forbid them to leave the house, or send them to their room and keep them there, and indeed generally restrict or even proscribe their movements, and as kidnapping effectively involves the exercise of these powers then I cannot see how the offence can be charged against a parent. Can anybody help?