Germany's top court has declined to hear a series of challenges to the European Central Bank's bond-buying stimulus program, referring them instead to the European Court of Justice.

The dpa news agency reports Tuesday that those against the program claimed it constituted illegal budget financing and that Germany's central bank should not be participating.

The Federal Constitutional Court ruled that because the challenge was about European Union regulations, it was up to the European court to decide.

The ECB's 2.28 trillion euro ($2.7 trillion) bond-purchasing program is only due to run through 2017, raising the question of whether the case can be heard before the program has already ended.