[gjulianm]

Calling for secession is not directly a criminal offense. The charges were sedition and misuse of public funds. The latter is fairly clear, the former is a more gray area (in Spain, sedition is a public tumultuous rising to stop laws from applying, using violence or illegal methods) and one could debate whether it applies or not. But in both cases, the reasoning was that the Catalan government did not have the competence to hold that referendum, was notified of that by legal means and they disobeyed those orders. That was the core of the decision, not about the contents of the referendum but the fact that they didn't have the authority to do it and did it nevertheless.

> and that the central government should have (a) staged the referendum and (b) campaigned in it.

When some people think that giving Catalonia enough entity to even consider independence is too much, a referendum is out of the question. If the central government had been open to hold the referendum they would also have been open to previous smaller claims from Catalonia that would probably have satisfied enough people and dropped support for independency.