Ponsati, 62, handed herself in at a police station in Edinburgh before a scheduled court appearance to face a sedition charge stemming from Catalonia's unsanctioned referendum.
A small group of demonstrators displaying Catalan and Scottish independence flags and banners greeted her outside St Leonard's police station.
Madrid first attempted to extradite the St Andrews University academic, a former education minister in the regional government of deposed Catalan president Carles Puigdemont, last year.
But a Spanish Supreme Court judge abruptly dropped European and international arrest warrants for her and several other separatist leaders in July, 2018.
However, the same court on October 14 sentenced nine Catalan separatist leaders to lengthy prison terms over the failed 2017 independence bid and issued a fresh arrest warrant for Ponsati.
She has branded the charge “a prosecution with political motivations”.
“We believe this is an abuse of the extradition process,” her lawyer Aamer Anwar said outside the police station.
“The crime of sedition is a 16th-century offence”, he added, noting it was abolished long ago in Scotland.
“We will be fighting this on the basis of Clara's human rights being abused if she is returned back to Spain.”
‘It is not a crime to vote for independence, I will continue to to fight for freedom & to expose Spanish injustice” @ClaraPonsati Once again Clara takes on the Spanish state with its unlimited resources in our courts?- please donate & share https://t.co/5UH3krTOcP pic.twitter.com/TZQ9aNc03v
— Aamer Anwar?✊? (@AamerAnwar) November 14, 2019
Ponsati's legal team is expected to apply for bail at the afternoon hearing at Edinburgh Sheriff Court.