Brussels - Former Catalan president Carles Puigdemont is facing extradition proceedings in Germany after being held on a European Arrest Warrant issued by Spain over his role in his region's controversial independence drive.

Here are some key facts about the European Arrest Warrant.

- What is an EAW ? -

European arrest warrants were introduced in 2004 to replace lengthy extradition processes within the EU and to remove political interference, making it easier to return fugitives suspected of serious crimes.

They can be issued for crimes where the maximum penalty is at least one year in prison or where the fugitive has already been sentenced to at least four months in prison.

The judicial authority and police in the receiving country, in this case Germany, are sent the warrant and tasked with arresting and returning the suspect.

Map of Europe showing trips made by Carles Puigdemont during his self-imposed exile

- How long does the process take? -

After arresting the suspect, the country has a maximum of 60 days to send the wanted person back, though in practice most people held under European arrest warrants are returned much more quickly.

In 2015, Germany took an average of 15 days to return suspects who agreed to be sent back and 42 days for those who fought extradition. German courts turned down only 12 percent of EAW cases.

- Can Germany reject it? -

There are a number of situations in which courts can refuse to extradite under an EAW -- for example if the suspect has already been judged for the same offence, or is a minor or if the offence is covered by an amnesty.

A country can also refuse extradition if the suspected offence is not recognised under its own national law.

Rebellion was removed from the German penal code in 1969 or 1970, but German media have suggested the offence of "high treason" could apply instead.

Statistically most EAW applications are successful. In 2015 German courts turned down just 195 out of 1,610 cases -- around 12 percent.

Across Europe, out of the 140,000 warrants issued between 2005 and 2014, 38 percent of suspects were found and nearly three-quarters of them were extradited, official EU figures show.

Timeline of the Catalonian political crisis

- What happened in Belgium? -

Puigdemont fled to Belgium in October to avoid charges in Spain, prompting Madrid to issue an initial EAW against him.

There was speculation the EAW would fail because the Spanish offence of "rebellion" does not exist in Belgian law. The Beglian judges could have extradited him to face other charges -- including misuse of public funds -- on condition he would not be charged with rebellion.

But Spanish prosecutors wanted to avoid this so they could charge him with rebellion, so they withdrew the EAW in December, before the Belgian court ruled on it.