Even having a visa does not guarantee entry to the host country. The border crossing authorities make the final determination to allow entry, and may even cancel a visa at the border if the alien cannot demonstrate to their satisfaction that they will abide by the status their visa grants them.
Some countries which do not require visas for short stays may require a long stay visa for those who intend to apply for a [[residence permit]]. For example, [[
== Visa extensions ==
Some countries have [[Reciprocity (international relations)|reciprocal]] agreements such that a visa is not needed under certain conditions, e.g., when the visit is for [[tourism]] and for a relatively short period. Such reciprocal agreements may stem from common membership in international organizations or a shared heritage:
* All citizens of [[
* The United States [[Visa Waiver Program]] allows citizens of 38 countries to travel to the USA without a visa (although a pre-trip entry permission, [[Electronic System for Travel Authorization|ESTA]], is needed).<ref>https://esta.cbp.dhs.gov/esta/WebHelp/ESTA_Screen-Level_Online_Help_1.htm#vwp3</ref>
* Any [[Cooperation Council for the Arab States of the Gulf|Gulf Cooperation Council]] citizen can enter and stay as long as required in any other GCC member state.
* having a low risk of overstaying or violating visa terms in the country potentially granting visa-free entry
To have a smaller worldwide diplomatic staff, some countries rely on other country's (or countries') judgments in issuance of visas. For example, [[میکسیکو]] allows citizens of all countries to enter without Mexican visas if they possess a valid visa of the [[USA]] (on which an entry has already been granted to the USA). [[Costa Rica]] accepts valid visas of [[Schengen agreement|Schengen]]/[[
Visa-free travel between countries also occurs in all cases where passports (or passport-replacing documents such as laissez-passer) are not needed for such travel. (''For examples of passport-free travel, see [[Passport#International travel without passports|International travel without passports]]''.)