Crown of Glory: Europe in the Age of Napoleon, the player controls one of the crowned potentates of Europe in the Napoleonic Era, wielding authority over his nation's military strategy, economic development, diplomatic relations, and social organization. It is a very thorough simulation of the entire Napoleonic Era - spanning from 1799 to 1820, from the dockyards in Lisbon to the frozen wastes of Holy Mother Russia.
Perhaps you have units that remained selected in the other province (inside a container) while selecting units in the new province? Giving an order in this case will give the order to all selected units. Check the Orders icon on the riflemen and see if they were detached in England and then moved north; if so, then I would guess that that's what's going on.
I haven't been able to duplicate it, but admittedly I haven't tried it with riflemen yet.
Yeah, remember that spacebar or right-click on an empty space should deselect all units. It does sound like that's the problem, but let us know if it isn't.