Any Member which has ratified this Convention shall, in
so far practicable, advise its nationals on the possible problems
of signing on a ship register in a State which has not ratified the
Convention, until it is satisfied that standards equivalent to those
fixed by this Convention are being applied. Measures taken by the
ratifying State to this effect shall not be in contradiction with
the principle of free movement of workers stipulated by the treaties
to which the two States concerned may be parties.