An Austrian court has found it legal for an animal rights protester to wear a cow mask despite a ban on face coverings, in a "freedom of expression" decision hailed by activists.

The Constitutional Court upheld the protester's complaint against his fine for handing out flyers in support of animal rights while wearing the mask in the town of Baden.

The man, named by the Association Against Animal Factories (VGT) as David Richter, had been trying in June 2018 to draw attention to conditions for animals in the dairy industry.

A statement from the court dated last week and seen by AFP on Wednesday, said an exception to the ban on full-face coverings should be made in cases where someone is "exercising freedom of expression".

"In the exercise of this right the use of stylistic devices (here: an animal mask) must be allowed," it said.

According to the VGT, Richter was initially fined €150, which was reduced to €70 by a lower court.

VGT spokesman Martin Balluch said the NGO was "very happy" with the ruling as animal masks were "essential" for the group's protests.

"Hopefully this decision means that the repeated bans and penalties over the use of masks will be a thing of the past," he said.

"Animal rights activists have time and again been victims of the face-covering law, which had a completely different objective".

The ban on wearing masks in public came into effect in October 2017.

While aimed at the Islamic face veil, it was drafted to cover all face coverings in order to avoid challenges on the basis of religious discrimination.

However, carnival masks or coverings for medical reasons, such as those which have now become legally mandated in public places due to the coronavirus pandemic, are tolerated.