What is meant by “no more favourable treatment” for ships of non-ratifying countries?

These words appear in Article V, paragraph 7, of the Convention. The idea, which is also found in IMO Conventions, is that ships must not be placed at a disadvantage because their country has ratified the new Convention.

The practical consequence comes out clearly in the port State control provisions of Title 5 of the Convention, under which ships of all countries (irrespective of ratification) will be subject to inspection in any country that has ratified the Convention, and to possible detention if they do not meet the minimum standards of the new Convention.