Constitutional practicability of referendum on EU Constitution

No. Binding referendum requires implementation by constitutional amendment. Consultative referendum can anyhow be held if ordered by ad-hoc-law.

Regulation about a special transference of power to EU

none

Approval of transfer of sovereignty without effect of constitutional amendment

Majority of votes from both chambers, Art. 23 I 2 ConstGermany.

Approval of transfer of sovereignty with effect of constitutional amendment

Majority of 2/3 from the members of parliament and 2/3 of votes from the senate, Art. 23 I 3, 79 II ConstGermany. Limit of transfer is the "clause of eternity" for the fundamental principles of the constitution, Art. 23 I 3, 79 III, 20 ConstGermany.

Approval of constitutional amendment

Majority of 2/3 from the members of parliament and 2/3 of the votes from senate, Art. 79 II ConstGermany.

Other constitutional regulations about referendums

Referendum mentioned in Art. 29, 118 ConstGermany for a new formation of the federal states. Art. 20 ConstGermany mentions expressly that the people practise their sovereignty besides election and through special organs of legislation and execution by holding referenda.