Mont. Code Ann. § 25-9-610
25-9-610 Procedure for recognition of foreign-country judgment
25-9-610 . Procedure for recognition of foreign-country judgment. (1) If recognition of a foreign-country judgment is sought as an original matter, the issue of recognition must be raised by filing an action seeking recognition of the foreign-country judgment.
(2) If recognition of a foreign-country judgment is sought in a pending action, the issue of recognition may be raised by counterclaim, cross-claim, or affirmative defense.