Calling the decision a "political assault," Bwin official Manfred Bodner told reporters that his company would file a lawsuit claiming damages against Saxony.
State officials on Thursday revoked the betting license and banned the company from advertising its services. They cited a March ruling by Germany's highest court that upheld a state monopoly on gambling in Germany while calling on states to do more to combat gambling addiction.
Saxon officials added that the ban is effective throughout Germany's 3-billion-euro ($3.8 billion) gambling market as Bwin's license was based on the Saxon permit.
East German license
Despite the state monopoly, Bwin -- formerly known as Betandwin, argues that the license, which was issued by the outgoing former East German government in 1990, remains valid. Bwin has about one million customers in Germany.
According to Reuters news service, Bwin shares fell 9.1 percent to 20.90 euros ($26.80) following the announcement, extending a 31 percent drop on Wednesday after a German newspaper reported Saxony would withdraw the license.
The company has already lost 89 percent of its market capitalization in the past three months.
Germany's state monopoly has long come under criticism, including from the EU commission, which questions whether restrictions on private gambling companies is in line with EU's competition laws.