These moves seem legal since there is no mention in the manual regarding the movement options of an army that is already taking part in a campaign. But perhaps I missed something, otherwise a player could move his/her army beyond it's established borders.
So how do these examples seem to you ?
1. An army or a part of that army abandons a campaign in progress and moves to a friendly province.
2. An army or a part of that army abandons a campaign in progress and attacks an enemy province (or another neutral province).