Germany's parliamentarians are still wrestling with the question of how Anis Amri, the rejected Tunisian asylum seeker who committed the only major Islamist attack in Germany ever — was able to escape the law and carry out the Christmas market attack in December 2016 despite a string of petty crime convictions, several failed asylum applications and agents who had noted that he was being radicalized.

Several parliaments in Germany, both state and federal, are running parallel investigations. However, on Monday members from three opposition parties in Germany's federal parliament, the Bundestag, called a press conference to denounce a major obstacle: Germany's federal intelligence agencies — the domestic Verfassungsschutz (BfV), which is tasked with tracking political extremists around the country, and its foreign counterpart, the BND.

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Konstantin von Notz of the Green party, Martina Renner of the socialist Left party and Benjamin Strasser of the neoliberal Free Democratic Party said they would appeal to the Federal Court of Justice to get access to intelligence agency files — or, specifically, to find out which files on the case had already been sent to the parliamentary oversight committee.

Who watches the watchmen?

The Bundestag launched a fresh investigation into the Amri case in early March. In the months that followed the 2016 attack, it was revealed that Germany's state and federal security forces had made a series of mistakes. Intelligence agencies were criticized for failing to track Amri before the attack, even though he had been identified as a potential threat, and had indeed briefly been in custody for drug dealing. Moreover, immigration offices faced scrutiny because Amri had apparently been able to register as an asylum seeker under various aliases and nationalities.

"The core question is: what information did the government pass on to the parliament?" said von Notz. "It's noticeable when the account of events that we got from the Interior Ministry at the time was wrong, or at least contained serious gaps."

"We've often noticed a kind of defensive reflex when it comes to the question of the intelligence agencies," Strasser added.

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The three MPs also complained that the government was pursuing "salami tactics" about disclosing information on the Amri case — especially when it comes to the role of domestic intelligence.

"You might remember that in the first few days after the attack we were told, 'Amri took drugs and watched porn films, so how should we know that he was an Islamist?'" said von Notz. "And now they establish that for years he was under the focus of all the agencies and had contacts with radicals. The idea that the government has a tactical relationship with information — that is certainly a theory one could develop."

The political pressure on investigations into the failures of German authorities when immigrants commit crimes, already consistently high, intensified last week with the killing of a 14-year-old girl, allegedly by an Iraqi asylum seeker with "tolerance" status in Germany.

But the role of the domestic intelligence agencies in the Anis Amri case throws up other uncomfortable parallels — investigations into the neo-Nazi terrorist organization the National Socialist Underground (NSU), which murdered at least 11 people over a seven-year period, also revealed that BfV agents and informants knew, or should have known, about the group before the killings took place.

"It is at least interesting when it turns out that one or another informant was closer to perpetrator than was claimed by the government after the attack," said von Notz.

"The suspicion that informants did not present all the information they had is certainly in the air," said Strasser. "There was an informant who was in Amri's circles."

Trusting parliament

And yet, the three opposition parliamentarians on Monday said, the counterparts on the investigative committee from the two parties in government – Chancellor Angela Merkel's conservative Christian Democratic Union and the center-left Social Democratic Party — had blocked attempts to get ahold of intelligence agency documents.

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The situation was slightly absurd, von Notz told reporters, because the documents in question were already available to another parliamentary committee — the intelligence agency oversight committee, the PKGr.

The Green party MP also rejected suggestions made by the government that parliamentarians are prone to leaks. "The parliament also has a responsibility to keep these documents secret," von Notz said. "That is obvious. And this accusation that always comes from the government, that the parliament is Swiss cheese and so it shouldn't be told anything, is absurd — and malicious."