The chief of Interpol stated on Tuesday that the organization has made significant progress in stopping Russia and other countries from abusing its “red notice” system, which allows a nation to request that another country arrest a suspect, and that there is not much more that can be done at this time to make it better.

Legal experts, human rights organizations, and others have long claimed that nations such as China and Russia take advantage of the red notice system by utilizing it to extradite political opponents.

Interpol, the 195-nation worldwide police coordination organization, has stepped up measures throughout the years to stop the misuse of red notices; currently, all red notice requests are screened before being issued. Each year, over 10,000 are distributed.

“If I got good advice for example from NGOs (on) what else I can do, I would implement that,” Interpol Secretary General Juergen Stock told Reuters in an interview on the margins of his organisation’s annual General Assembly, which is being held in Vienna this year.

Stock, who is German, has another year in his mandate after nine years in the post.

“We have a small percentage, maybe 2%, 3% of tricky notices. The overwhelming majority concerns murderers, rapists, drug smugglers and what have you,” he said.

“Have we made one or the other mistakes perhaps where we had to correct a decision? Yes. I’m not saying it’s perfect but I’m saying it’s very robust,” he said.