Well, the constitution grants the judiciary branch the final say on all cases of legality. So I don't think it's very controversial that they also have the final say on the legality of the legislative and executive branch's doings.
Also of course, this is exactly the separation of powers, which is completely fundamental in all western societies.
Obviously it's not controversial now because that's how things have been done for more than 200 years, but the Constitution is far from explicit that they have that power.
Also of course, this is exactly the separation of powers, which is completely fundamental in all western societies.