Because it is fair.

Slovene student

• Slovene public education must be accessible to all citizens of Slovenia. This is only possible if it's in Slovene, because knowledge of other languages ​​is not equally accessible to all. Some ​​are less gifted for language learning or don't have the opportunity to learn languages. Universities are part of public education, therefore the knowledge they offer shouldn't be conditioned by the knowledge of foreign languages. 
  
• Slovene public has the right to be informed about the achievements, financed from the state budget − that is achievements that Slovenes are paying for with their own money. This information is most readily in their first language. And universities receive funding from the state budget ...
  
• Last but not least, the Slovene legislation requires Slovene as the language of instruction in higher education.
  

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