The first case happened last July, when a 15-year-old girl was threatened with jail because of aggressive begging and her refusal to pay a fine.
She had received a letter summoning her to 24 hours detention, despite the fact that it is illegal in Austria to jail under-16s for refusing to pay a fine.
When authorities came under criticism at the time, the district head said it was an isolated incident and police officers had simply failed to realise the age of the girl.
However an almost identical case emerged this week when a 15-year-old beggar in the same city was threatened with 66 hours behind bars for reportedly not paying a fine for spitting and smoking.
A third case in the nearby town of Bludenz also saw authorities threaten a 14-year-old girl with detention.
The lawyer in the latest case in Dornbirn, Anton Schäfer, said that it was a clear attack on Roma community that the boy belongs to and that authorities should be looking to help the children rather than fine them.
Schäfer also noted that the cases come as Vorarlberg and other states attempt to crackdown on begging in cities.
“You can clearly notice that the handling [of begging] is becoming rougher,” he said.
District head of Dornbirn Helgar Wurzer said that in this case the letter summoning the 15-year-old to 66 hours in detention should also have not been sent out.
A two person check will be carried out in future to ensure the mistake does not happen again, according to Wurzer.
According to a report in the Kurier, however, the fine against the 15-year-old has not yet been retracted and the boy could be summoned again to jail when he turns 16.