在UK，一个运动员可以代表谁（英格兰、威尔士、苏格兰、北爱尔兰）参加比赛应该由什么决定？

关于球员的代表队选择问题，详见国际足联最新版本的章程《FIFA STATUTES》：

全文第二部分：Regulations Governing the Application of the Statutes 中，第三章：为代表队参赛资格（III. Eligibility to play for representative teams）就说明了：

5. Principle

1. Any person holding a permanent nationality that is not dependent on residence in a certain country is eligible to play for the representative teams of the assiciation of that country.

本人英语不好，不过基本的意思还是明白的：

任何拥有该国国籍的公民，无论你在该国是否有住址（其他国家不清楚，在英联邦或曾是英联邦国家里的地区，居住证明是很重要的，起码开银行卡需要这货），都有代表该国（country）代表队的资格。

以下是针对上述准则的补充说明。首先是一国多足协的情景：

6 Nationality entitling players to represent more than one association

1. A player who, under the terms of art. 5, is eligible to represent more than one association on account of his nationality, may play in an international match for one of these associations only if, in addition to having the relevant nationality, he fulfills at least one of the following conditions:

a) He was born on the territory of the relevant association;

b) His biological mother or biological father was born on the territory of the relevant association;

c) His grandmother or grandfather was born on the territory of the relevant association;

d) He has lived continuously on the territory of the relevant association for at least two years.

最后的d)项是针对居住地的情况作出说明的。

再者是多国籍的选择规定：

7 Acquisition of a new nationality

Any player who refers to art. 5 par. 1 to assume a new nationality and who has not played international football in accordance with art. 5 par. 2 shall be eligible to play for the new representative team only if he fulfi ls one of the following conditions:

a) He was born on the territory of the relevant association;

b) His biological mother or biological father was born on the territory of the relevant association;

c) His grandmother or grandfather was born on the territory of the relevant association;

d) He has lived continuously for at least five years after reaching the age of 18 on the territory of the relevant association.

另：国际足联对联合王国四大足协做了特别的补充说明：

Each of the four British associations shall be recognised as a separate member association of FIFA.

所以按照联合王国的国情：

对于英国籍球员来说，只要满足第6点中任意一个条件即可：

1. 自己出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
2. 生母/生父出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
3. 奶奶/爷爷出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
4. 在英格兰/苏格兰/威尔士/北爱尔兰居住满两年或以上。
   

对于英国之外国籍的球员，则要满足第7点中的任意一个条件：

1. 自己出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
2. 生母/生父出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
3. 奶奶/爷爷出生在英格兰/苏格兰/威尔士/北爱尔兰；
   
4. 18周岁后在英格兰/苏格兰/威尔士/北爱尔兰居住满五年或以上。

因此个人觉得，国籍和个人意愿都是必需品，但是都要按照FIFA的规定来。不过更多时候，球员的意愿往往是占了上风的。

要说具体案例的话，我就知道两个比较典型的例子：王老吉和孙大圣。死神出身地在威尔士卡菲利且在威尔士长大，不具备讨论性。

• 王老吉在威尔士出身，成长居住都在英格兰。他原本可以代表英格兰出战，且曾经代表过英格兰学童队参赛，却因为母亲的缘故最后选择了威尔士。


• 孙大圣的祖母是英格兰人，但他觉得为威尔士出战“是一份无尚的光荣”，后来也如他所愿。
  

更多的具体案例，例如斯特林的例子（出身在牙买加，他妈妈希望他为牙买加效力）还望各位知友补充。

另附国际足联章程《FIFA STATUTES》原文：

补充一点联合王国四大足协的小知识（该问题之前有知友在知乎中问过）：