Constraint is related to Limit. Limit is related to Barrier. Barrier is a synonym of Obstacle. 
Import is a different concept from Domestic. Domestic is similar to Municipal. Municipal is a synonym of Civic. 
Constraint <--RelatedTo--> Limit <--RelatedTo--> Barrier <--Synonym--> Obstacle 
Import <--DistinctFrom--> Domestic <--SimilarTo--> Municipal <--Synonym--> Civic 