If im understanding your question right then the answer is no...... Example A Umbreon can be obtained in Platinum, but its original region was Jhoto. i can still migrate that Umbreon to my pokemon Black even though its in the Shinnoh Region.
Source-Personal Experience
If you mean you migrate a pokemon from one region can you migrate it again the answer is yes you can still migrate it again.......Example i have a Charmander on my Firered and i migrate it to my Heartgold, later i can migrate that same Charmander to my pokemon Black.
Source-Personal Experience