The sole reason behind the police keeping someone in custody is to protect for the mean time the suspect pending the time he or she is guilty.
Yes it is the right of the police, given to them by the law is protect the juveniles and make sure they are kept safe until the next date to appear in court, should in case it is a court case. This law is backed up by the law.
The President in the executive branch can veto a law, but the legislative branch can override that veto with enough votes. The legislative branch has the power to approve Presidential nominations, control the budget, and can impeach the President and remove him or her from office.