[citation needed] At the time of the treaty, agreements signed between representatives of the monarch had to be registered at the King's Council.

That essential formality was never performed, but it seems that, on many occasions, French civil law recognised the validity of the agreement.

The treaty has always been fairly applied in practice and is referred to in the following texts: The inhabitants of the French side of St. Martin will enjoy the ability to consume and export abroad salts harvested by them on the Dutch side, this under the terms of the Treaty of 1648.The requirements of the Decree shall not apply to foreigners from the Dutch island of St.Martin regarding their stay and transit in the French part of the island.

Foreigners from the islands of Saba, Anguilla, Statia, Saint Christopher Nevis, which at the date of this Order were finally fixed in the dependences of Saint-Martin and Saint Bartholomew for the benefit referred to in the preceding paragraph.There currently is a movement in both Sint Maarten and Saint Martin for the unification of the island, which would invalidate the Treaty of Concordia.

It has been proposed that the freedom of movement allowed by this treaty may have made possible the development of a common identity by the inhabitants of both halves of the island.