Sorry for the delay in response. I forget the question
Hipotetical situation: Nationalist player controls Cantabrico and Baleares naval boxes.
1. Oviedo, Bilbao and Barcelona is considered blockaded?
Yes. The efect of the naval boxes, is the same of a blockade for naval units.
2. Republican player can't play any cards which bring into play units in Oviedo, Bilbao and Barcelona? Or he can play cards which is not assotiated with ports (such cards as #6 "Basque Army" or #1 "Anarchist mobilisation")?
The republican player only can play cards not asociated with ports in this cities.A port is "cosiderated not friendly" for the efect of blockade, or control of naval boxes.
Can play card: 39, 28, 27, 24, 22, 18, 15, 7, 6, 1.