"You cannot just assume that every departure to Syria means participation in a terrorist combat unit," said Innsbruck criminal lawyer Andreas Venier. The guilt must be proven in every case, he added. The two girls, Samra K. and Sabina S., disappeared from Austria in April.
According to their parents, Bosnian refugees who arrived in Austria during the 1990s, they announced that they wanted to fight in Syria for Islam.
The two teens supposedly travelled to join jihadist militants in Syria, and were in the news recently when one of them was reported to have died. Soon after, they took to social media to report that they were both still alive, and hinted that they might be pregnant.
With recent reports suggesting that the two teenage girls have had second thoughts about their jihadist fighter husbands, and are now wanting to return home to Austria, speculation is mounting on how the Austrian government should treat them.
While it's unlikely that they would face severe penalties, unless it can be proven they have engaged in terrorist activities, some form of criminal case is still likely.
According to Interpol, the girls are still officially missing, and may be being held against their will. Officially, Austrian authorities have made no comment.
Recently, however, the government made it clear that participation in a terrorist organization - such as Isis - will be punished if fighters or their supporters return to Europe.
As minors, the two would face a maximum penalty of five years in prison, however there are potentially mitigating circumstances, said Venier, if it can be shown they were intimidated or seduced into joining the terrorist group.
"About 150 people, most of whom have Russian citizenship and are believed to be Chechens, have travelled from Austria to take part in conflicts in Syria and Iraq," Peter Gridling, director of the Federal Office for the Protection of the Constitution and Counter Terrorism, said in an interview to the Kleine Zeitung newspaper.
In addition, a number of others with Turkish, Bosnian, Egyptian, Macedonian and Serbian backgrounds have also taken part in the conflicts, he said, adding that 15 to 20 percent of them are believed to have Austrian citizenship.
"Additionally, there are an even larger number of people in the country - perhaps thousands - who either approve of the activities of these individuals or are not explicitly opposed to them, although they would not necessarily commit themselves to terrorist plots," he added.
The director pointed out that most Muslims in Austria are opposed to terrorism, and most mosques and prayer houses are not believed to be part of the radicalisation process, with only 20 of the 360 such establishments in the country causing concern.
With regard to whether Isis would attack Europe, he said that as long as the military advances of the group are stopped, there is no reason for it to make strikes in Europe.