International laws are not based on any authority of one country over other country.
International laws are based on mutual agreements, reciprocity and in spirit of cooperation between countries.
One country has no right to impose its local laws on staff working in embassy of other countries.
There are crimes against humanity and there are crimes, which are not crime as such, but are declared crime by laws passed by local law making body.
Violation of crimes in second category of above cannot be treated as “Crime” for the purpose of International law.