This is the 9453rd most frequent French word.
douanières
"Douanières" means "customs officers" or "related to customs."
In this sentence, 'douanières' is used as an adjective modifying 'contrôles' (checks), indicating that the checks are related to customs operations.
Les contrôles douanières sont nécessaires pour assurer la sécurité nationale.
Customs checks are necessary to ensure national security.
Here, 'douanières' is an adjective describing 'réglementations' (regulations), highlighting its link to customs policies.
Les réglementations douanières peuvent changer selon les accords internationaux.
Customs regulations may change according to international agreements.
Again, 'douanières' acts as an adjective here, qualifying 'formalités' (formalities), which relates to administrative procedures required by customs.