the WHO has no power as such, see their mission statement below:
healthydocuments.org/appendices/doc49.html
The objective of WHO is the attainment by all peoples of the highest possible level of health. Health, as defined in the WHO Constitution, is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. In support of its main objective, the Organization has a wide range of functions, including the following: To act as the directing and co-ordinating authority on international health work; To promote technical co-operation;
To assist Governments, upon request, in strengthening health services;
To furnish appropriate technical assistance and, in emergencies, necessary aid, upon the request or acceptance of Governments;
To stimulate and advance work on the prevention and control of epidemic, endemic and other diseases;
To promote, in co-operation with other specialized agencies where necessary, the improvement of nutrition, housing, sanitation, recreation, economic or working conditions and other aspects of environmental hygiene;
To promote and co-ordinate biomedical and health services research;
To promote improved standards of teaching and training in the health, medical and related professions;
To establish and stimulate the establishment of international standards for biological, pharmaceutical and similar products, and to standardize diagnostic procedures;
To foster activities in the field of mental health, especially those activities affecting the harmony of human relations.
WHO also proposes conventions, agreements, regulations and makes recommendations about international nomenclature of diseases, causes of death and public health practices. It develops, establishes and promotes international standards concerning foods and biological, pharmaceutical and similar substances.