Certain crimes have been found to involve a higher ratio of foreigners than others. These include smuggling, currency offenses, unlawful crossing of frontiers, and traffic offenses. Counterfeiting and drug trafficking have increasingly become problems. For alien offenders with diplomatic immunity, the rules of the Vienna Convention apply. Treatment of other alien offenders generally follows the substantive and procedural rules prescribed by internationally accepted provisions on cooperation and the treatment of alien offenders (i.e., the Treatment Doctrine and The International Minimum Standard for the Treatment of Aliens). While the most appropriate principle for the handling of alien offenders is that requiring a transfer of penal procedure to the alien