Pundits in the region believe that the activation of Article 155 may lead to further civil unrest in Catalonia, following mass protests before and since the controversial independence referendum on 1 October.
After Catalonia's leaders on Thursday defied an ultimatum from Madrid by failing to abandon their push for independence, Spanish Prime Minister Mariano Rajoy called an extraordinary cabinet meeting for Saturday, where the government is expected to invoke a never-before-used article of Spain's constitution to reduce some of the region's autonomy.
"Despite some disquiet over the way Rajoy handled a Catalan independence referendum on Oct. 1, which Madrid said was illegal and sent in police to disrupt voting, countries fear making any remarks that could embolden separatists at home".
Catalan universities are among the country's best: of the top five Spanish universities in the annual ranking compiled by the Shanghai Ranking Consultancy, three are Catalan - Pompeu Fabra, the University of Barcelona and the Autonomous University of Barcelona.
The Treasury had aimed to sell between 4 billion and 5 billion euros of the four bonds.
Catalonia's debt represents 35.4 percent of GDP, which made it the third most indebted region in Spain in the second quarter of 2017 - owing around 76.7 billion euros ($90.2 billion).
The 10-year benchmark, due Oct 31, 2027, sold 1.0 billion euros at an average yield of 1.627 percent and with demand outstripping supply by 1.8 times.
It is thought the measures implemented could range from taking control of the regional police and finances to calling a snap election.
"The only thing I am asking Mr. Puigdemont is that he act sensibly, that he act with balance, that he puts first the interests of all citizens, of all Spaniards and all Catalonians", Rajoy said.
It added that Madrid "deeply regrets the attitude of those responsible for the [government] of Catalonia to seek, deliberately and systematically, institutional confrontation". It also represents about one fifth of Spain's economy and one seventh of its population.
Located in northeastern Spain, near the French border, Catalonia has its own language, culture, and traditions.
The commission criticises the manipulation of the composition of the Polish Constitutional Court, given that it can create legal uncertainty and political controversies, which undermine the legitimacy of their sentences. Have you or have you not declared the independence of Catalonia? They include Catalan banks and large to medium-sized businesses.
The Catalan crisis is reaching breaking point but we have to be careful here. Hai Do was the editor.
"There is not much to gain from backing Barcelona and a lot to lose from angering Madrid", said a senior EU diplomat at the EU summit.
Meanwhile, the commission criticises the dominant role of the parliament in the election of members to the self-governing institution of Polish judges. The situation is "serious but not unexpected".