Europe's highest court has ruled that stem cells from human embryos cannot be patented, in a case that could have major implications for medicine.
Scientists say the decision by the Court of Justice may impede European research into the use of stem cell therapies, or drive research abroad.
The BBC reports the ruling follows a challenge by Greenpeace over a patent for nerve cells from embryonic stem cells.
Embryonic stem cells have the ability to turn into any tissue in the body.
They offer the hope of one day being able to treat diseases such as Parkinson's, stroke, heart disease and diabetes, if technical hurdles can be overcome.
The ruling concerned a method invented by Professor Oliver Bruestle of Germany for converting human embryonic stem cells into nerve cells.
The court's decision had been seen as critical for research into the use of stem cells as treatments for a range of diseases.
In a statement, the European Court of Justice said:
"The use of human embryos for therapeutic or diagnostic purposes which are applied to the human embryo and are useful to it is patentable.
"But their use for purposes of scientific research is not patentable."
It added: "A process which involves removal of a stem cell from a human embryo at the blastocyst (early embryo) stage, entailing the destruction of that embryo, cannot be patented."