Alexander Hamilton added that a Bill of Rights would "contain various exceptions to powers not granted; and, on this very account, would afford a colorable pretext to claim more (powers) than were granted. ... (it) would furnish, to men disposed to usurp, a plausible pretense for claiming that power." Going back to our picnic example, those who would usurp our God-given liberties might enact a law banning our right to have a picnic. They'd justify their actions by claiming that nowhere in the Constitution is there a guaranteed right to have a picnic.
To mollify Alexander Hamilton's and James Madison's fears about how a Bill of Rights might be used as a pretext to infringe on human rights, the Ninth Amendment was added that reads: "The enumeration in the Constitution of certain rights shall not be construed to deny or disparage others retained by the people." In essence, the Ninth Amendment says it's impossible to list all of our God-given or natural rights. Just because a right is not listed doesn't mean it can be infringed upon or disparaged by the U.S. Congress. The Tenth Amendment is a reinforcement of the Ninth saying, "The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people." That means if a power is not delegated to Congress, it belongs to the states of the people.
The Ninth and Tenth Amendments mean absolutely nothing today as Americans have developed a level of naive trust for Congress, the White House and the U.S. Supreme Court that would have astonished the founders, a trust that will lead to our undoing as a great nation.