"This is a matter entirely for the judicial authorities whose independence we respect fully," European Commission spokeswoman Annika Breidthardt told journalists.
The comment came on the same day as the German government expressed its full support for Madrid following the detention of eight former Catalan ministers over their role in the region's independence drive.
"From the federal government's point of view, Spain is of course a state governed by the rule of law and as government spokesman I see no reason at all to comment on decisions made by Spanish courts," Steffen Seibert told reporters following the controversial move on Thursday.
"We continue to support the clear position of the Spanish prime minister (Mariano Rajoy)," Seibert said.
"What's important to us is that the unity and constitutional order of Spain are maintained."
Tensions have soared in Spain after a large chunk of Catalonia's axed government was thrown behind bars on Thursday pending probes into their role in the secession push.
A Spanish judge was also Friday set to issue an EU arrest warrant for Catalonia's deposed leader Carles Puigdemont, who is holed up in Belgium.
The European Union and its member states have been resolute in their support for Madrid throughout the crisis.
Spain has been plunged into turmoil since Puigdemont's government organised an independence referendum on October 1st despite a court ban.
A declaration of independence by the Catalan parliament followed last Friday.
But the same day, Rajoy dismissed the regional government, imposed direct rule on Catalonia and called regional elections for December 21.