It is a democracy only so far as we vote on our representatives, who then vote on our laws.
Only at the state level, and only occasionally, do the people directly decide what laws we have.
The constitution, especially in the bill of rights, specifies any number of limits on the government, federal and state.
If by that you mean...
- A table of organization
- A list of powers granted to each organization created above
- A list of limits on same
...then yes.
At the moment.
Then you need to pass a bunch of amendments.
How's that going for you?