You won't be able to EV train them. You can still check their IVs though. Use the EV reducing berries to get rid of any EV they may have gained in any battles. You can look them up through google or something. There are 6, one for each stat. When you use them to get rid of all EVs, you can accurately check for IVs through their lv 100 stats. It takes 11 of each EV reducing berry to get rid of all EVs IF over 100 EVs are in one stat.
For example, if you have 164 EVs in one stat, you use one EV reducing berry to lower it to base 100, then 10 berries to reduce EVs to zero.