In european futball, can a player play for any other team of any other country?

The rules are similar, inside of Europe if a player is from a country that is a member of the European Union then the person can work anywhere in the EU without a work permit as long as the team and player can agree to terms. (Just as a person from Texas can take a job in New York.) For players outside of the the EU they have to pass certain requirements to get a work permit (the equivalent of a U.S. Green card) or claim citizenship by having a parent/grandparent that was a citizen of that country or whatever requirements that country has to claim citizenship. Each country can set up their own rules for what is required from say a Brazilian to or an American to come over and play for a team in Europe.