The European Court of Human Rights (EHRC) has rejected an appeal by Turkey's parliamentary main opposition party challenging a referendum held earlier in the year that will increase the powers of the president.
The court ruled that the case did not fall under its jurisdiction, according to the decision published on Thursday.
President Recep Tayyip Erdogan's "yes" camp won the April 16 referendum on a series of constitutional amendments with a thin margin. The opposition Republican People's Party, or CHP, contested the outcome of the vote, citing a number of irregularities, including the Turkish electoral board's decision to count as valid unstamped ballots in violation of the law.
According to an ECHR statement, the CHP argued the referendum took place under unfavourable and undemocratic conditions.
"Referendums, unlike elections, are not held at reasonable intervals owing to the fact that in most, if not all cases, they represent a system of ascertaining the opinion of the people on a matter that is not a recurrent subject, such as the constitutional referendum in the present case," said the court.
"Secondly, and importantly, referendums are not usually organized as a means of electing citizens to certain posts, in other words, as an election giving the electorate the possibility to choose the legislature," it said.
"In the present case, although the constitutional referendum introduced many significant changes to the constitution, the people of Turkey were clearly not choosing any particular person or persons for a legislative post or posts," it added.