Kreshnik B. became the first Islamist taken to court in Germany for allegedly fighting with "Islamic State" terrorists in Syria. The 20-year-old German with Kosovar roots is currently on trial in Frankfurt. If he cooperates with the authorities and shows remorse, he faces a milder juvenile sentence of four years and three months in jail.

Now politicians and German security agencies want to intervene in the issue of German Islamists heading to Jihad in Syria or Iraq before a trial becomes necessary. They are discussing measures to stop German Islamists leaving the country for the war zones in the Middle East or to prevent their re-entry into Germany.

Considering the roughly 400 Islamists who traveled to Syria from Germany since 2012, this is an urgent question. But not everything that authorities are demanding can legally be put into action.

Cancelling the passport

Conservative politicians from Chancellor Angela Merkel's Christian Democratic Union demanded for example that Islamists who fought in Syria should not be allowed back into the country. But under German passport law, "a German must never be denied entry into the area of this law's application."

And according to a study by the BND, Germany's domestic intelligence agency, that looked at the 400 Islamists who traveled to Syria from Germany in detail, more than half of the extremists have a German passport. So to spring into action only when they want to return from their jihad is probably wrong.

One possible preventative measure is to confiscate the passport. "If there's a danger to public safety or order, taking away the passport is admissible," Frankfurt lawyer Reinhard Marx told DW. In exigent circumstances, confiscation can be enforced immediately, and without a passport, the alleged extremist fighter can't travel outside Europe.

Marked for special treatment

But that doesn't solve the problem. After all, Germans can travel the EU and some other countries with their personal ID-card as well. Countries they can enter this way include Turkey and Egypt, easy entryways into Syria or Iraq.

"First and foremost we need international cooperation - in certain states like Turkey, but also inside the European Union," German Interior Minister Thomas de Maiziere said.

Because the personal ID-card cannot be confiscated, politicians are now considering marking it, according to German daily Die Welt. This mark would then identify the owner as someone who is not allowed to leave Germany.

"If we have information about a German Islamist who wants to go to jihad to learn how to kill, then we must take his passport away and mark his ID-card accordingly," Thomas Strobl, vice-head of the CDU, told the paper.

Cancelling dual citizenship

According to the BND's study, 92 of the 400 extremists who traveled to Syria have at least one other citizenship. Is it easier to prevent these people from re-entering Germany by just taking their German citizenship away?

"The German citizenship held by someone in addition to another one is by no means of inferior quality," Marx said. "It follows the same rules as the 'regular' German citizenship and is just as protected."

So far, joining another country's armed forces is the only permissible reason to revoke their German citizenship.

Now politicians want to change that. Strobl demands that the law be extended to include parties in a foreign civil war, like "IS." This would give Germany a tool to fight at least some of its returning Islamists.