A German parliamentary inquiry looking into US National Security Agency (NSA) spying in Germany initially decided it would not invite whistleblower and former NSA contractor Edward Snowden, who leaked the documents revealing the US intelligence agency's massive spy programs, to testify in Berlin.

The Green and Left opposition parties on Friday requested that the German Constitutional Court, the country's highest legal institution, rule on whether Snowden should testify in front of the inquiry committee in Berlin to provide a "global overview of the technical conditions of mass surveillance," according to Greens lawmaker Konstantin von Notz.

Although the German government appears not to want to risk harming its relationship with the US by allowing Snowden to speak in Berlin, inquiry committee members from Germany's governing parties have said they also want to hear from Snowden. They, however, want to do it via video link or in Russia, where Snowden currently lives in exile, rather than in the German capital.

Opposition members may have to wait years for a ruling

Snowden has requested Germany ignore a standing US extradition request and provide him with security guarantees if he were to travel to the country.

Snowden is wanted by the United States for theft of government property and unauthorized communication of classified intelligence. The German government has argued that allowing Snowden into the country would endanger national security by threatening German-American relations. For his part, Snowden has refused to testify from Russia.

Now it's up to the justices of Germany's Constitutional Court to decide "whether we, as parliamentarians, can exert our oversight function or whether the federal government and intelligence services control oversight," said Martina Renner of the Left party. She called for the inquiry's hearings to be made completely open to the public.

The opposition parties leveled their suit at the German government and its party members in the parliamentary inquiry as a constitutional dispute between government institutions for the Constitutional Court to rule on. But a final ruling could take years, according to attorney of record Astrid Wallrabenstein, a law professor at Frankfurt University.

The German government said Snowden did not meet its asylum criteria

Exactly what is in the suit has not yet been announced. Greens politician Christian Ströbele said the court should have time to become acquainted with the material before taking it to the public.

The opposition parties hope the court will rule that the government did not provide adequate evidence to back up their claim that Snowden's testimony in Berlin would endanger national security.

"You have to take a stand," the Left party's Andre Hahn said, explaining the lawsuit's short-term purpose. "This can't continue the way it has - as it stands, we cannot clear up anything."

The government on Friday referred questions to a statement it made in May that the conditions necessary to grant Snowden asylum in Germany had not been met. This statement will likely also make up part of the evidence the Constitutional Court will have to evaluate.