Obama is moving towards imprisoning children and teenagers that cross the US border without papers.

The crucial point is that it is feasible to expel these people without keeping them in prison while their cases are decided.

If the US wants fewer minors from Central America to cross the border, it might be more effective to run a campaign to inform the public in Central America that getting over the US border does not, as they have been told, give you permission to stay in the US.