The Hague Abduction Convention normally applies only if the Convention is in force between the country of the child's habitual residence and the country in which the child is currently located.

However, the Dutch Implementation Act, pursuant to which the Hague Abduction Convention was brought into Dutch law, provides that the Implementation Act also applies in non-treaty cases of international child abduction. 
Article 2 states that, “This Act provides for the implementation of the conventions referred to in article 1 and also applies in cases of international abduction of children that are not governed by a convention.” 
Article 13(3) of the Implementation Act provides that in such cases the court may refuse the request for return on the grounds stated in Article 12, Article 13 and Article 20 of the Convention.
Thus, the Dutch Central Authority and the Dutch courts treat cases of abduction to the Netherlands from a non-Hague country in the same way as if the child were removed from a Hague Convention treaty partner.
From a global perspective, this is extremely unusual.

Our office has worked on many matters concerning the abduction of children to the Netherlands, always collaborating with local counsel in all jurisdictions as appropriate.

Disclaimer: We are admitted to practice only in New York but work as appropriate with lawyers throughout all U.S. states and throughout the world.