Welsh clubs Swansea City and Cardiff City have been told by Uefa the only way they can qualify for Europe is by representing the English league.
Swansea and Cardiff are among six Welsh clubs in the English system and there had been uncertainty they could qualify for Europe via the English pyramid.
But both have been given assurances by European football's governing body.
Uefa's executive committee have ruled Welsh clubs in an English league cannot qualify for Europe via the Welsh Cup.
This means Swansea can play in Europe if they finish in the Premier League's Europa League places.
The Welsh Cup was first awarded in 1877 to Wrexham, who have won it a record 23 times
Uefa, though, did reject the
Football Association of Wales' request
to give their six exiled clubs a promise of European football through the Welsh Cup.
Uefa's two-day executive committee meeting in Istanbul has finally clarified that Swansea, Cardiff or any of the Welsh clubs would qualify for Europe should they finish high enough in the English top flight or by winning the FA or League Cups.
"Welsh clubs, like Swansea and Cardiff, will be able to qualify for European competition through the English system," confirmed a Uefa spokesman.
The Swans are eighth in their first Premier League season, just 10 points behind fifth-placed Chelsea, while Cardiff were FA Cup finalists in 2008 as well as 2012 League Cup finalists.
Clubs that finish fifth in the Premier League will definitely qualify for the Europa League but if the FA Cup final is between two clubs in the top five, a sixth-place top-flight finish will then earn a Europa League spot.
Swansea could also earn Europa League qualification through the Fair Play League but only if the English league is in the top three national associations in the Uefa Fair Play ranking.
Tottenham Hotspur currently lead the Premier League's fair play table but if Spurs, who are third in the Premier League, qualify for the Champions League, a possible Europa League place would go to the team second in that table which is currently Swansea.
However, the Premier League seems unlikely to earn a Fair Play European place this season.
Uefa's ruling is a blow to the Welsh FA who wanted to offer Welsh clubs competing in the English league pyramid, also including Wrexham, Newport County, Colwyn Bay and Merthyr Town, the carrot of Europa League qualification to persuade them to play in the Welsh Cup.
Newport, Wrexham and Merthyr entered this season's Welsh Cup
but their participation in future Welsh Cups may now be in some doubt without the lure of European qualification.
Wrexham, winners of the Welsh Cup a record 23 times, beat Cardiff 2-1 in 1995 in the last Welsh Cup final involving Wales' English league clubs.
Wales' exiled clubs had been barred from entering the competition since 1995 when Uefa initially insisted only clubs from the Welsh league system were eligible to represent Wales in Europe.
"We accept the decision and as an association we'll move on to strengthen the profile of the competition as it exists at the moment," said FAW spokesman Ian Gwyn Hughes.
"I think everybody would accept since the likes of Cardiff and Swansea ceased playing in the Welsh Cup the profile has dropped.
"But it's up to us as an association working with those clubs to improve the strength and the profile of the competition within the clubs that play in it."