A "bill of rights" is a piece of paper. A piece of paper which is ruled upon by a court that was granted its power by the very same collection of papers.
For example, the right to keep and bear arms (obviously not for hunting but for war and security) has been infringed upon many times, but constitutional courts have decided that actually despite the bill of rights, some infringement is allowed. (EDIT: And this doesn't even address the problem of governments creating unconstitutional laws or executing unconstitutional actions which de facto strip your rights for some possibly significant time until it can be overturned by a court, but without much redress or punishment or deterrent)
In the end the people are the ultimate arbiters and deciders of what rights they are willing to give up and what powers they are willing to be governed under. This plays out the same way in USA and Australia and Afghanistan and Libya.