He is now in the EU
No, he's not. He's in the Canaries, which are outside the EU customs area.
Just like any other criminal, he can be deported as part of his sentence or immediately after serving any time of penal servitude.
The people who really need their arses kicked are the airport authorities in Western Sahara who refuelled the aircraft and let it go. They should have placed a pair of armoured vehicles to block the aircaft from moving and called in the appropriate special forces to sort the bastard out.
No aircraft should be permitted to depart under the control of a hijacker.