A transfer can be fully agreed between two clubs and still fail because the player cannot legally work in the country. Immigration approval is a distinct process that clubs cannot negotiate around.
The permit is granted by the state, not the league
Employing a foreign athlete requires authorization from the destination country's immigration authority, issued against criteria set in law rather than by the sport.
Clubs and governing bodies can endorse an application, but endorsement is a recommendation within a system that ultimately answers to national policy.
Rules vary by country and change over time, so a deal structure that worked for one signing may not be available for the next.
Criteria usually measure international experience
Many systems assess a player against objective measures such as appearances for a national team, the standing of the selling league and the fee involved.
Players who fall short can sometimes be considered through an appeal process where a panel judges whether they are of exceptional quality.
The effect is a bias toward established internationals and against young players from leagues the criteria rank lower, regardless of how good those players are.
Nationality and residency create exceptions
Dual citizenship frequently solves the problem outright, which is why family heritage becomes relevant in transfer reporting in a way it otherwise would not.
Some countries have arrangements with neighbors or former colonial partners that treat certain nationalities differently, and clubs plan recruitment around those routes.
Time already spent legally resident can also change a player's status, so a move within the same country carries none of the risk of an inbound one.
Age rules restrict international transfers separately
The world governing body restricts international transfers of minors, with narrow exemptions covering family relocation and certain cross-border regions.
That regulation exists independently of immigration law, so a young player can be legally resident and still ineligible to register for a club.
Breaches have led to registration bans for clubs, which makes compliance a matter clubs handle conservatively rather than testing the limits.
Why this matters when reading a rumor
A report that a deal is agreed says nothing about whether the player will be permitted to play, and the gap between those two things has ended many transfers.
Specific requirements differ by jurisdiction and are revised regularly, so any assessment of a particular case needs current information about that country rather than a general rule.
The reliable signal is a club's recruitment pattern. A side that signs repeatedly from a small set of countries is usually working within permit criteria rather than expressing a preference for those leagues.