Here is the content of Newropeans' proposal on the trans-european referendum:

2. Ratify systematically the main changes of community treaties, and in particular enlargements by trans-European referenda.

To allow citizens to decide the main future orientations of the EU
to avoid having an elite, disconnected from the citizens and peoples, impose its choices. These trans-European referenda will use a double majority in order to ensure democratic respect of minorities: more than 50% of the votes cast across the whole of the EU and more than 50% of the Member States voting in favour would be necessary to secure passage of a proposal.

As you can see one country can not block the others.
best
David