Durk wrote:I assume MP means a unit with a Police factor?
No: the Military Police
ability, as Andatiep wrote (those elements for sure have a Police factor too, and a good one).
Some units such as common cavalry elements may have a Police factor, they can be used for this but are not really trained for; they won't be able to counter desertions (they don't have the ability round in bottom of the detailed numbers).