4. The President may, in the case of a bill passed by both the Reichstag and the Reichsrat in agreement, use his right of veto; that is to say, he need not promulgate the law but must refer it to a referendum. In that case the law does not become operative unless the referendum supports the vote of the Reichstag. If the referendum pronounces against it the law is definitely rejected. The Constitution does not say whether the President may, in such a case, propose a change in the bill and submit this change to another referendum. We must consequently conclude that he cannot do so. 5. If one-twentieth of the electors demand that a law already passed by the Reichstag shall be submitted to a referendum; and if, at the same time, at the demand of one-third of the Members of the Reichstag the promulgation of that law has been deferred, the latter cannot go into effect except after having been approved by a referendum. If the referendum pronounces against the bill, the latter is rejected. But this possibility does not exist in the case where both the Reichsrat and the Reichstag have declared a law to be urgent. The President may in such a case promulgate the law in spite of the demand for its postponement. 6. There remains finally the exceptional case in which a popular initiative by one-tenth of the electors proposes the project of a law. In such a case the law, if it is accepted by referendum, becomes operative, whether the bill has been passed without change by the Reichstag, or, with changes by it, or even in spite of the Reichstag’s rejection. It is thus seen that a referendum is never resorted to, unless the Reichstag has first taken a vote on the subject. The decisions of the people appear, therefore, as a kind of control over, and check on, the Reichstag’s decisions. The procedure just described is that followed for all ordinary laws.[38] In theory it holds also for _constitutional laws_, that is, laws which, according to the Constitution, must be enacted in the form of constitutional laws; but there are certain modifications in the procedure in such cases. Under the old Constitution, changes in it could be brought about by the same means as ordinary laws. The new Constitution places constitutional law under special protection, and demands that a certain fixed majority be obtained for any change in the Constitution. Decisions of the Reichstag tending to such a change are not valid unless two-thirds of the legal number of members are present and of those present at least two-thirds vote for such change. In the same way decisions of the Reichsrat tending to a change of the Constitution must obtain a majority of two-thirds of all the votes cast in their favour.