Spanish 'art 155' unlawful?

Before you start reading, this is my first post here, so any suggestions on how to improve my posts are welcome...

As you probably know, people in Catalonia have recently organized a referendum for independence from Spain. The Spanish government has violently opposed this referendum, calling it illegal and void, and has reacted by activating an article in their constitution, thereby removing the Catalan government from power, and temporarily disabling the Catalan autonomy.

The Spanish government follows in this discussion a very legalistic approach - but just how lawful is the law? If you follow a legalistic approach, you have to respect international treaty's first, constitution second and common law last...

An independent expert at the UN has published his opinion here:
http://www.ohchr.org/EN/NewsEvents/Pages/DisplayNews.aspx?NewsID=22295:

“Denying a people the right to express themselves on the issue of self-determination, denying the legality of a referendum, using force to prevent the holding of a referendum, and cancelling the limited autonomy of a people by way of punishment constitutes a violation of Article 1 of the ICCPR and of the International Covenant on Economic, Social and Cultural Rights. (...) [The principle of territorial integrity] cannot be invoked to quench the right of all people, guaranteed under Article 1 of the International Covenants on Human Rights, to express their desire to control their futures. The right of self-determination is a right of peoples and not a prerogative of States to grant or deny."

Spain is, like all other European countries, a state party in this international treaty. In fact, respect for this treaty is a major requirement to be a member of the EU, and the European Commission has the duty to warn, publish or intervene if a member country violates human rights. So - what's the European Commission waiting for?