In French law, Certain goods pay higher export duties when exported to a foreign country than when they are destined for another French port. In order to prevent fraud, the administration compels the shipper of goods sent from one. French port to another to give security that such goods shall not be sent to a foreign country. The certificate which proves the* receipt of the security is called “acquit d caution* Argles, Fr. Merc. Law, 543
Source: Black's Law Dictionary 2nd Ed (1910)
