With Britain leaving the European Union, there are new laws as of January 1 - and that means new regulations in next month's transfer window, which could have previously restricted the signings of Paul Pogba, Cesc Fabregas and Hector Bellerin among others.
Premier League clubs are to be limited to three U21 signings each transfer window with all foreign players subjected to a point-based threshold to be eligible to play in the UK.
Players from European Union countries will not be allowed to be signed without a work permit while foreign players under the age of 18 cannot be bought at all as part of post-Brexit regulations, meaning Premier League clubs will have to wait to secure the services of top young talent from abroad.
Why are the rules being introduced?
When the United Kingdom leaves the European Union, Premier League clubs will be unable to sign players freely from the EU as the UK will no longer have access to the Union's single market of free movement of labour.
What is a Governing Body Endorsement?
Football authorities have agreed a plan of entry requirements for overseas players with the Government. The Football Association, the Premier League and the English Football League submitted a Governing Body Endorsement (GBE) proposal last month, which has now been approved by the Home Office.
The criteria will provide the framework for clubs to sign overseas players when the UK leaves the European Union after December 31.
How have they come about?
The regulations outlined by the Premier League, FA and EFL are designed to safeguard the future of the England national football team, while also allowing domestic clubs to remain competitive and have the ability to sign players of high quality.
The authorities have been in dialogue for some months over the exact entry requirements for transfers from overseas.
What are the entry requirements?
The criteria were based on the player's appearances in international matches and their country's FIFA rankings. The higher number of appearances and the higher the nation's ranking, the more points the player in question will have.
A player from a top-10 FIFA-ranked country who has featured in over 50 per cent of that nation's matches in the last two years would enable a player to sign for a Premier League club with a GBE. But for those players representing lower-ranked countries, they will have had to have played almost all matches in order to score enough points.
Furthermore, how a club performs in a competition is weighted in earning points. If a player gets 15 points, they will earn a GBE.
Can exceptions be made?
Yes, a player may obtain a GBE through subjective criteria if they are unable to tally enough points. An Exceptions Panel, made up of people from different stakeholders in the game, will in these cases assess the application. The player must be classed as of "the highest quality" to be permitted a GBE.
In addition, if a player earns between 10-14 points, his case will automatically be sent to the Exceptions Panel.
What are the key rules?
Clubs will be restricted to just three overseas signings under the age of 21 from January onwards, and only six foreign players per campaign moving forward.
Post-Brexit, players from EU countries will be required to gain a GBE, like the work-permit system for other overseas players.
The GBE will operate a points system based on senior and youth international appearances, club appearances and the quality of the selling club and its league.
Players accumulating the requisite amount of points will earn a GBE automatically, while players just below the threshold may be considered for a GBE by the Exceptions Panel.
Will this lead to more homegrown players?
The FA has also proposed to use Brexit to amend the "homegrown" rule and cut the number of foreign players allowed in Premier League squads post-Brexit.
The FA is eager to reduce the number of non-homegrown players allowed in a squad from 17 to 13 but the Premier League will fight to maintain its standards on quality.
Post-Brexit immigration will undoubtedly impact football transfers involving the Premier League, and it remains to be seen just how the various challenges posed will shape the transfer strategies of clubs heading into 2021.
Who are Europe's wonderkids?
Premier League clubs will be unable to buy foreign players under the age of 18 from January, due to post-Brexit regulations. That means some of these rising stars will be out of reach to Premier League sides until they are 18...
Alejandro Iturbe - Atletico Madrid, 17
Iturbe is considered by many at Atletico to be the heir to Jan Oblak's throne as first-choice goalkeeper in the future. The youngster was called up by Diego Simeone to train with the senior squad during pre-season and is currently playing for the Juvenil A team - Atletico's U19s. Iturbe doesn't turn 18 until next September.
Ilaix Moriba - Barcelona, 17
The central midfielder currently plays for Barcelona B and doesn't turn 18 until January 19. Moriba is regarded as the best player at La Masia and has been likened to Paul Pogba in sections of the Spanish media. Born in Guinea, Moriba represents Spain internationally, having recently played for their U18s.
Naci Unuvar - Ajax, 17
Unuvar has already played and scored for the Ajax first team on his debut and is the latest talent to emerge from the club's famed youth system. Teenagers Ryan Gravenberch and Lassina Traore having already made their mark on the first team, and with Unuvar not turning 18 until June, Premier League club won't be allowed to prise him away from Amsterdam.
Which players would not have been signed...
Some Premier League star names joined their clubs when they were under 18 in the past. Here are a few of the deals which wouldn't have been possible under the new regulations...
Hector Bellerin - Barcelona to Arsenal
The Premier League's top academies are preparing for life after Brexit - and one club who have benefited from the European Union's exception to a FIFA rule are Arsenal. English clubs will only be able to sign foreign talent when they have turned 18.
Bellerin, now in his seventh season as first-choice, joined along with Barcelona team-mate Jon Toral at 16 in 2011.
Paul Pogba - Le Havre to Man Utd
Manchester United signed Paul Pogba at 16 from Le Havre, although he left three years later for Juventus. United had been cleared to sign the then-teenager after FIFA rejected claims by the French club that the player had been illegally induced to move to Old Trafford.
Eric Garcia - Barcelona to Man City
Manchester City will have to take a different approach on sustainability while using their academy when new Brexit rules are imposed. The club have made a healthy profit on signing players from the continent before they turned 18, helping their overall transfer strategy.
Having turned down a new contract, Garcia could leave for a reduced fee in January, joining the likes of Brahim Diaz (£15m), Pablo Maffeo (£8.8m), Rony Lopes (£9m) and Jason Denayer (£9m) in being sold having arrived before their 18th birthday - something which would not be allowed under the new rules.
Sepp van den Berg - PEC Zwolle to Liverpool
Liverpool agreed a deal with Dutch Eredivisie side PEC Zwolle to sign defender Sepp van den Berg when he was a 17-year-old back in June 2019.
Van den Berg was a Netherlands U19 international when made 15 appearances for Zwolle during the 2018/19 season - and the centre-back made four appearances under Jurgen Klopp last term across the League Cup and FA Cup.
Mikki Van Sas - Utrecht to Man City
Manchester City signed the highly-rated teenage goalkeeper Mikki van Sas from Utrecht to join their academy ranks last summer. The 16-year-old was linked with a move to Ajax but opted to move to the Etihad.
Jayden Braaf - PSV to Man City
Braaf signed for Man City on his 16th birthday in the summer of 2018 as a first-year scholar, joining from PSV Eindhoven having also spent time at Ajax's academy.
City fought off stiff competition from the likes of Manchester United, Chelsea and Bayern Munich for the signature of the young Dutch forward - but he would not be able to join the club's Elite Development Squad under the new regulations.
Federico Macheda - Lazio to Man Utd
Macheda shot to fame when he scored the winning goal for Manchester United against Aston Villa on his Premier League debut in April 2009. At the start of the 2007/08 season, he left Lazio as a 16-year-old to head to Old Trafford, leaving the Serie A club angry at seeing their star prospect snatched from their youth academy.
United were able to pull off the transfer as a result of regulations in Italy that prevented clubs from tying a player under the age of 18 to a contract - but the new post-Brexit rules would mean United needing to wait until a player's 18th birthday in order to make such a transfer.
Nicolas Anelka - PSG to Arsenal
Nicolas Anelka is the only player in Premier League history to score more than 20 goals with four different clubs (Arsenal, Bolton, Chelsea, Manchester City). But the Frenchman may not have made it to English shores were the new rules in place back in 1997 when he signed from Paris Saint-Germain at just 17 years old. Anelka won the PFA Young Player of the Year Award during the 1998/99 season before joining Real Madrid for £22.3m.
Cesc Fabregas - Barcelona to Arsenal
Fabregas reached 25 Premier League assists at a younger age than any other player, at just 20 years and 134 days.
But the Spaniard would not have arrived in the Premier League when he did as a 16-year-old under the new transfer rules. He went on to play over 300 games for the club before being sold back to Barcelona for £30m in 2011.