I agree the charge is quite serious, and the Supreme Court's sentence is accordingly very harshly worded and intended as exemplary.

Some of the issues here have to do with inconsistent enforcement. For instance, there's this commentary today: an expected coincidence

En las escuchas, todo se basa en una interpretación legal del artículo 51.2 de la Ley General Penitenciaria que permite la intervención de las comunicaciones de los presos "por orden de la autoridad judicial y en supuestos de terrorismo". El juez atendió la petición de la policía y las dos fiscales anticorrupción al adoptar la medida y luego fue prorrogada por el juez del TSJ de Madrid Antonio Pedreira. Ninguno de ellos ha sido molestado, ni siquiera han comparecido como testigos.

En otros procesos, como el caso de Marta del Castillo, se escuchó a los presuntos autores del asesinato para tratar de encontrar el cadáver de la joven; en el del abogado Pablo Vioque, se escuchó a su letrada para prevenir el asesinato del entonces fiscal jefe antidroga Javier Zaragoza, para lo que el preso había contratado a un sicario. Ninguno de los casos tenía que ver con el terrorismo, pero tampoco ninguno de los jueces fue molestado.

On the wiretaps, it all hinges on the legal interpretation of article 51.2 of the General Penitentiary Law which allows intercepting the inmates' communications "by judicial order and in cases of terrorism". The judge heeded the request of the police and two anti-corruption state prosecutors, and it was later extended by the judge of Madrid's Superior Court of Justice Antonio Pedreira. None of them have been bothered, they haven't even appeared as witnesses.

In other processes, such as the case of Marta del Castillo, the presumed authors of the murder were listened on to try to find the young woman's body; in the case of lawyer Pablo Vioque, his attorney was listened on in order to prevent the murder of the then anti-drug Chief Prosecutor Javier Zaragoza, for which the inmate had hired a henchman. None of these cases had to with terrorism, but also none of the judges was bothered.

This appears to hinge on the logical interpretation of and in by judicial order and in cases of terrorism.

The other issue is whether the conversations of a lawyer with someone who isn't their client (but is a defendant in the same case) are protected. They don't seem to be protected by attorney-client privilege but only by general privacy of communications.

tens of millions of people stand to see their lives ruined because the bureaucrats at the ECB don't understand introductory economics -- Dean Baker

I'm pretty sure that conversations about organizing money laundering aren't normally privileged. Even if you are ostensibly the defense lawyer.

These weren't attorneys, they were (allegedly) criminal co-conspirators.

If you're interested in the legal arguments for Garzon's defence, here is a blog quoting (and linking) the State Prosecutor's brief to the Supreme Court in support of the legality of the wiretaps (in cluding quotes of Constitutional Court jurisprudence). All in Spanish obviously. Google translation: Can a lawyer be recorded when they talk to their client? (yes, when you see how Google garbled the headline, reading the legalese is hopeless).

tens of millions of people stand to see their lives ruined because the bureaucrats at the ECB don't understand introductory economics -- Dean Baker

These cases have been 2-3 years in the making. I think it's just coincidental that the sentence happened to be handed down in the first 100 days of a new right-wing government.

After all, the elections would normally have taken place in March, had they not been brought forward by Zapatero to get himself out of the Euro crisis.

tens of millions of people stand to see their lives ruined because the bureaucrats at the ECB don't understand introductory economics -- Dean Baker