However, penalties exist for exercising foreign citizenship, such as identifying oneself to Polish authorities using a foreign identification document. Serving in a foreign military does not require permission of Polish military authorities, if the person resides in that foreign country and has its citizenship. Poland treats nationals of other countries whom it considers Polish citizens as if they were solely Polish. Because Polish citizenship is determined by the citizenship of a Polish parent without any explicit limitation for the number of generations elapsed abroad for descendants of Polish emigrants, which may create problems for individuals of Polish descent born abroad who, in spite of having no ties to Poland, are nevertheless subject to all obligations of Polish citizenship, formerly including military service (Poland suspended compulsory military service on December 5, 2008 by the order of the Minister of Defence and compulsory military service was formally abolished when the Polish parliament amended conscription law on January 9, 2009; the law came into effect on February 11). In addition, such individuals are not entitled to consular protection of their home country under Article 36 of the Vienna Convention on Consular Relations. The only exception is when a bilateral consular agreement calls for recognition of the expatriate citizenship, regardless of the allegations of Polish citizenship raised by Poland. Such an agreement was negotiated in the 1972 Consular Convention between the United States and Poland providing that: "Persons entering the Republic of Poland for temporary visits on the basis of United States passports containing Polish entry visas will, in the period for which temporary visitor status has been accorded (in conformity with the visa's validity), be considered United States citizens by the appropriate Polish authorities for the purpose of ensuring the consular protection provided for in Article 29 of the Convention and the right of departure without further documentation, regardless of whether they may possess the citizenship of the Republic of Poland." However, since Poland abolished visa requirements for United States citizens in 1991, this provision no longer applies. The problems resulting for members of the Polish diaspora, Polonia, from being treated by Poland solely as Polish citizens are compounded by the difficulty to renounce Polish citizenship (see above). Poland has been enforcing with varying stringency its claims to citizenship allegiance from descendants of Polish emigrants and from recent refugees from Polish Communism who became naturalized in other countries. Under a particularly strict enforcement