The European Union’s executive arm will monitor any agreement to set up so-called return hubs in non-EU countries so that the rights of rejected asylum seekers sent there are protected, the bloc’s migration commissioner said Friday.

Magnus Brunner said any such deal will also be vetted by the International Organization for Migration and the UN refugee agency to ensure compliance with those legal safeguards.

“Human rights standards and international law is non-negotiable,” Brunner told a news conference during a meeting of EU migration ministers to mark the implementation of the bloc’s new migration and asylum pact.

The return hub concept is just one of the new pact’s provisions that have been met with skepticism from human rights groups that question whether these centers could turn into long-term holding facilities overflowing with failed asylum seekers stuck in legal limbo.

Greece repeated Friday that it is one of five EU members, along with Germany, Austria, Denmark and the Netherlands, that is negotiating with African countries to set up such return hubs on their territory.