The treaty, ratified by China's Standing Committee of the State Council, the top legislature, is the first treaty of its kind China has signed with an EU member.

According to the treaty Chinese nationals who are convicted in Spain can be returned to China to serve jail sentences and Spanish convicted criminals in China have the same right.

The treaty also says criminals will not be subjected to new sentences after being transferred to their motherlands and their original sentences will not be changed, but if the crimes and the span of the sentences don't comply with local laws, criminals will be rendered new sentences.

A source with the Chinese Ministry of Justice says criminals serving jail sentences in foreign countries is not conducive to rehabilitation or jail management due to different language, culture and conventions, adding that such cooperation helps to resolve the problem.

"The transfer is based on the will of criminals, " the source says.

Spanish ambassador to China Jose Pedro Sebastian de Erice told Xinhua that justice cooperation between China and Spain is a crucial part of their strategic partnership, revealing two nation's mutual trust and respect.

Erice says the Spanish parliament has ratified the treaty and will put it in operation in 30 days after the two countries exchange ratification certificates.

"The treaty is helpful for criminals to back to society and it is a sign of human rights respect,' Erice says.

China and Spain have stepped up the pace on justice cooperation in recent years.

In July 2005, the two countries signed a treaty, vowing to beef up their criminal law cooperation and in November, the two sides inked an extradition treaty.

The treaty was signed by Foreign Ministry Vice Minister Zhang Yesui on 14, November 2005 in Madrid.