'Opposition' there is used in the parliamentary sense. In a parliament, there there is usually a ruling party or coalition, which acts as a government and the other parties act as an opposition. The opposition typically votes against legislation that they politically disagree with, and often tries to find any faults with the way the government operates.

I agree with Merlyn. In contrast with the other comment, it's irrelevant whether the country is a parliamentary democracy or not.

The government is not allowing anyone to speak out againt the government.