The court dismissed the argument by referendum petitioner Vili Kovačič that the chosen date meant discrimination against those who would want to engage in the campaign because it would start before the end of summer holidays.

Under Slovenia's election and referendum campaign act, official campaigning can begin at the earliest 30 days ahead of the voting day and end 24 hours before the voting day when the election blackout sets in.

The Constitutional Court noted that only the first quarter of the campaign would be held during summer holidays and parliamentary recess, and all the relevant dates fall into the final holiday week when it is reasonable to expect most of the voters will have been back to their daily routines.

The National Assembly determined the date of the referendum on 4 July. The opposition wanted the vote to be held together with the presidential election due sometime later in the autumn, which they said would save EUR 3m in costs.

The cost factor was also brought up in Kovačič's petition, but the court said the argument was not specific enough for it to be able to test.

Unhappy with what he called a contradictory decision, Kovačič said that two constitutional judges voted against. "We'll see about our next steps, but the case may go to the European court," he said.

In his dissenting opinion, judge Marko Šorli disagreed with the view that having a quarter of the campaign time during holidays would not materially affect the efficiency of the campaign.

Similarly, his colleague Klemen Jaklič dissented by saying that the court's decision was not good for anyone, not even for trust in the institution that took such a decision.

He said that moving the date to the first Sunday after 24 September or any of the following Sundays would mean no part of the campaign as an integral part of the right to vote in a referendum was held during holidays.

Parliamentary Speaker Milan Brglez hailed the Constitutional Court's decision, noting that seven of the nine judges had voted for it. He described the dissenting opinions as interesting, saying he would examine them in more detail.