The HSE was not entitled to discontinue funding for a quadriplegic Irishman receiving treatment in Germany just because he had been there for 11 years, according to a preliminary opinion by an Advocate General of the European Court of Justice.
in 2002, Peter Flood suffered a rare brain injury while on holidays there, resulting in severe quadriplegia.
Since then he has received treatment from consultants attached to a clinic in Dusseldorf, and has been further diagnosed with cancer and blood issues.
Since his discharge from hospital in 2003, he has lived in an apartment where he is cared for by his girlfriend.
He receives a disability allowance from Ireland and a small occupational pension from the UK, but receives no allowance or benefit from Germany.
The HSE met its obligations to fund Mr Flood's care until 2011.
At that point, it argued that by virtue of the length of his stay in Germany, he was now a resident there, and that the German state should be liable for the cost of his care.
It announced that it would stop covering the cost of his treatment, at which point Mr Flood took legal proceedings.
He argued that it was his wish to return to Ireland, but he is compelled by his illness to remain in Germany for his ongoing treatment.
He said he had at no time intended to change his residence from Ireland to Germany.
He has no bank accounts in Germany, does not speak the language, has worked very little since his illness and has made no attempt to integrate into German society.
His girlfriend was refused the equivalent of a carer's allowance in Germany on the grounds that Mr Flood was an Irish resident.
Both sides accepted it was almost impossible for Mr Flood to travel, at least by scheduled airlines.
The Advocate General said the case raised the thorny issue of whether a member state like Ireland could "export" to other member states the cost of providing medical treatment to its residents.
He said it was not entirely clear that it would be possible for Mr Flood to receive comparable treatment in Ireland.
He said the HSE had stated "rather paradoxically" that the cost of treating Mr Flood in Germany is considerably lower than the cost of treating him in Ireland if her were to return.
Advocate General Wahl of the ECJ found that the forced stay for 11 years in another member state due to grave illness which first manifested in that member state did not in itself mean that the person could no longer be regarded as merely staying in the treatment country.
He said an insured person could not simply being excluded from the social security system to which he had previously been affiliated with no forewarning.
He said that a forced stay did not entail that the place of treatment which had hitherto been the temporary centre of the person's interest, automatically became the place of habitual residence.
The Advocate General stated that it was for the referring court in Ireland to establish the place of residence of the person on the basis of an overall assessment of all the relevant circumstances.
He said that would include whether that person remains compelled on medical grounds to stay in the country providing medical treatment in order to receive the necessary treatment.
Mr Flood's solicitor Claire Callanan said he was delighted with the outcome.
She said the unilateral HSE decision had caused him additional trauma on top of his already extensive disability.
She said they would now await a final decision of the European Court of Justice but noted that in over 80% of cases, the full ECJ follows the preliminary opinion of the Advocate General.
At that point, the case will revert to the Irish High Court for a final determination.
The HSE noted that the Advocate General of the ECJ had issued an opinion on the legal point that was referred to the ECJ by the Irish High Court.
However, it stated that the ECJ has not yet issued a ruling on this case.
It said that while the ECJ will consider the AG's opinion it has yet to determine the question posed by the Irish High Court and then the matter goes back to the Irish High Court for determination.
The HSE said that as the matter remains sub-judice it cannot comment at this time.