D. Subsequent State Practice
When interpreting a treaty, the Vienna Convention confirms that
subsequent state practice that establishes what the agreement was between the
States Parties can be taken into account: "There shall be taken into account,
together with the context: any subsequent practice in the application of the treaty
which establishes the agreement of the parties regarding its interpretation."7 0
Therefore, if States Parties are acting as though they do have transnational
prevention obligations arising from the Protocol, this will evidence their
intention to be bound by mandatory obligations in Article 9(4).
This section reviews transnational prevention programs and initiatives that
the major countries of destination have implemented since ratifying the Protocol.
The countries or regions that are discussed are: Australia, Canada, Europe and
the United States.7' The purpose of this analysis is to seek to establish whether
these countries have been operating on the assumption that they have shared
responsibility to prevent trafficking in countries of origin.
Admittedly this interpretive approach requires a logical leap that some
readers may find troubling. We must assume the State Party considers itself
legally bound by international law rather than simply morally bound or
motivated by domestic politics. Accordingly, the State practice explained below
does not confirm nor deny what the motivation for this practice was. The fact
that these practices were only introduced after the creation of the Protocol tends
to support the contention that these States considered themselves legally bound
by the Protocol. However, admittedly this connection is tenuous and could also
be explained by politics or even a subjective moral imperative.