I suggest finding out exactly why they have to go. If it's a good reason then their health status would be the next question, together with things like age, number of lambings and if they've been running with a ram. If you decide to take them I would recommend checking them over thoroughly before you fetch them back (condition, teeth, feet, udders for lumps), quarantining them for at least three weeks, giving them an orange or purple wormer (watch out for withdrawal times if you plan to have them slaughtered or send them to cull) and put them on your vaccination programme.