Pupils from Northern Ireland have been told they qualify for free tuition in Scotland if they have an Irish passport.
The announcement serves to complicate an already confusing system which allows European Union citizens to study in Scotland for free, but charges other UK students up to £9,000 a year.
The loophole in European Union law, which stipulates EU students outside the UK must be treated as locals, means Scottish students and EU students pay no fees, while students from Wales, England and Northern Ireland pay the full sum.
This means students from Ireland - which is outside the UK - can qualify for free tuition in Scotland.
The dual nationality available to students in Northern Ireland opens up another loophole. Sixth formers applying for some courses in Scotland have been told they qualify for free tuition, regardless of where they live, as long as they hold an Irish passport, according to the BBC.
Cathy Moore, chair of the Careers Teachers' Association, said: "The Scottish Parliament has said if you have an Irish passport and live in Northern Ireland and provide that, (Irish passport) you are eligible to have the fees paid."
Scotland has seen a 6% rise in the number of EU students applying to its universities to study this autumn, while applications to other UK universities fell by as much as 16.5%.
Concerns have already been raised whether Scotland's university fees system breaches human rights laws and this latest development will only fuel the fire.
Scottish education secretary Michael Russell blamed the confusion on the rise of tuition fees in England.
"We're in this position because of a decision not made in Northern Ireland nor in Scotland but south of the border on hiking fees south of the border.
"We decided in Scotland not to do that; to continue with the Scottish tradition of free education. Quite clearly we couldn't pay for everybody coming into us, so we've allowed the universities to set their own fee levels for those coming in.
"The purpose of the regulations is to guarantee Scottish students free access. It is not to find ways around for other people. Because of European law, people coming from other jurisdictions do get the same treatment as Scottish students but those in the rest of the UK don't."