If "international" refers to relating to or involving more than one nation:
* Domestic
* National
* Local
* Regional
If "international" refers to something that transcends national boundaries:
* Local
* National
* Provincial
* Domestic
If "international" refers to a group or organization that operates across borders:
* Local
* National
* Domestic
Therefore, the best antonym depends on the specific meaning of "international" in the context.