When the issue of Gibraltar’s membership in UEFA was first raised in 2007, Spain’s soccer federation threatened to pull its teams — including Real Madrid and Barcelona — out of European and international competition. That led FIFA to reject Gibraltar’s application for membership on the grounds that its stadium was built on a disputed territory. UEFA later changed its statutes to admit teams only from a United Nations-recognized nation state.

Gibraltar countered that several FIFA members — including Palestine, the Faroe Islands and even England — are not recognized nation states, either, and that it had applied for membership before the rules were changed.

The ruling on Gibraltar is not likely to be the last controversial addition to 2018 World Cup qualification in Europe. Kosovo, which fought a war for independence from Serbia in the late 1990s, also has been pushing for UEFA and FIFA membership.

Kosovo is recognized by a majority of European Union and United Nations members, but official recognition by those bodies and others has been elusive. Instead, Kosovo has sought legitimacy through sport. In 2014, the International Olympic Committee confirmed Kosovo’s membership, meaning it can compete under the Kosovar flag at the Olympic Games in Rio de Janeiro this summer.

Yet in soccer there has been fierce opposition to Kosovo joining UEFA and FIFA; Serbia views Kosovo as a historical part of its territory, while Russia, a Serbian ally, has vowed to use its United Nations Security Council veto if a vote is ever brought on Kosovo’s recognition.

The former FIFA president Sepp Blatter supported greater recognition for Kosovo, and the territory was granted permission to play friendly matches against other FIFA members in 2014. Its first match was a 0-0 draw against Haiti in the ethnically divided northern Kosovar city of Mitrovica.