Can I be arrested in Spain if my Red Notice was issued by a country with no extradition treaty?

Yes. Spanish police act on Interpol Red Notices regardless of whether Spain has a bilateral extradition treaty with the requesting state. You can be detained for up to 40 days while the requesting country formally submits an extradition request through diplomatic channels. However, without a treaty, Spain has no legal obligation to extradite and the Audiencia Nacional will assess whether to proceed based on reciprocity principles and international conventions. The absence of a treaty strengthens defence arguments but does not prevent initial arrest or detention.