AFP reports that on Friday, May 9, Microsoft lodged an appeal at a European court against a record 899 million euro (1.39 billion dollar) fine imposed on it by the EU Commission for defying a landmark anti-trust ruling.

Personally, I believe that such cases are the best justified ones in whole antitrust spectrum. As prof. D. T. Armentano once said:

Employing antitrust against legal barriers to entry enacted
by state and local governments may create incentives
to dismantle those barriers.
[Antitrust: The Case for Repeal (Auburn, AL; 1999): 62]

What are the legal barriers to entry enacted by state in this case? Intellectual Property, of course.