That's incorrect. The government has powers limited by the Constitution.The government has the powers given it in the Constitution. Technically, in a democracy the government has any powers a majority of the people choose to give it. That is why many make the point that we are not a democracy because a majority cannot override the rights of the minority in our system.
We can't, by popular vote, seek to outlaw a religion or enslave a group of people. Or can we? After all, we can dictate to people what drugs they can or can't take.