PARIS, Sept 6 (Reuters) - A Paris court is set to rule next month on whether a French regulator has the right to block access to international porn sites in France unless those sites can guarantee they can prevent minors under 18 from accessing them.

Following a complaint by children's rights associations, French audiovisual and digital regulator Arcom in December 2021 gave notice to five porn sites including Pornhub, requiring them to prove they were blocking access to minors in line with July 2020 French legislation.

An Arcom official said that since then the regulator had seen no indication the sites were putting in place systems that could really block access for minors, it decided to take legal action.

The four other sites being challenged by the regulator are Tukif, Xhamster, Xnxx and Xvideos.

The regulator said it wanted the court to order French internet service providers such as Orange, Free and SFR to block access to these porn sites on French territory until they have a solid system for blocking access to minors.

At a hearing on Tuesday, lawyers for the porn sites argued the court was not authorised to rule on the case as the law was not in line with the constitution. The court will now rule on Oct. 4 whether it can decide on the issue or whether the case needs to go to the appeals court, an Arcom official said.

Currently, porn sites in France only have to display a disclaimer button on which users can click to say that they are over 18, but there is no verification of their actual age.

An Arcom official said the sites - which are all free - would have to propose a free and reliable blocking system.

A lawyer for PornHub publisher MG Freesites did not immediately return calls for comment. She was quoted on French radio franceinfo as saying that verifying an internet user's age is technically and legally impossible.

In recent months, Arcom has also served notice to several other porn sites, including YouPorn, one of the world's top porn sites, the Arcom official said.

French children's rights associations have started several legal cases to block access to online pornography for minors, arguing that current age verification standards make it too easy for children to access the websites. (Reporting by Geert De Clercq Editing by Tomasz JanowskiAr)