France and the African Union oppose Azawad's independence

New state: Azawad

The actors are different but the reasons are the same: both France (and its satellite Spain) and the artificial post-colonial African states fear that the status quo of these unnatural states imposed on the reality of ethnicities and often also on the true will of the affected peoples will spread like an epidemic of sorts causing the collapse of the old world order. 

There are many other cases I can think of but this problem specially affects Southwestern Europe, which is still to enjoy the benefits of national self-determination as Central and Eastern Europe and even Ireland could achieve in the 20th century, and Africa, where states are in most cases nothing but capriciously drawn colonial administrative divisions.

North Africa faces the issue of the Berber minorities, demanding independence or at least greater autonomy in Algeria and Morocco specially, where they are more numerous, but the situation is totally dramatic south of the Sahara, where almost not a single polity approaches the modern concept of nation-state.

This issue has triggered long and/or bloody separatist wars by areas and ethnicities which find themselves disadvantaged in the states assigned, often dividing them in several arbitrary portions. Some of the most notable secessionist struggles have been:

• Casamance (vs. Senegal)
• Biafra (vs. Nigeria)
• Katanga (vs. Congo/Zaire)
• South Sudan (vs. Sudan, suceeded)
• Darfur (vs. Sudan)
• Eritrea (vs. Ethiopia, succeeded)
• Somalis in Ethiopia (vs. Ethiopia)
• Tuaregs (vs. Mali, Niger and Algeria)

There are also other cases  in which a territory has been more or less arbitrarily assigned to a neighboring country against the will of the people, even if the case of distinct ethnicity is not so clear. This is the case of West Sahara, whose military annexation to Morocco is mostly rejected, and of Somaliland, whose incorporation to Somalia was challenged more recently and has declared its independence unilaterally as well. 

And the dissatisfaction with the post-colonial political arrangements does not just manifest in secessionism and the occasional religious conflict but also in civil wars and other internal conflicts, which often run across ethnic lines. 

In fact it is scientifically demonstrated that ethnicities which have been divided as result of border-drawing suffer the most from all kind of conflicts, at least in Africa (though I'd dare say this applies to all). 

In brief: the Jacobin neocolonial regimes organized by the former colonial power, France, in the Francophonie and in general all the regimes produced by the scramble of Africa 130 years ago (and the unfinished decolonization of 50-60 years ago), associated in the African Union, fight and will fight by all means at their reach against the right of self-determination of the peoples in Africa as in Europe. 

However reality is gradually overriding their Jacobin dictates. Eventually, it is inevitable that the artificial borders are redrawn by the peoples themselves.