It was assumed to be there, because the Constitution limited the Federal government to only certain things and all other rights were retained by the people. It was only added as an amendment to ensure that it wasn't overlooked, as were all the other amendments.
Obviously: 'Right to bear arms'... was NOT in our Founding Fathers Constitution..
.. it is called the 2nd AMENDMENT for a reason. Took 15 years.
It was assumed to be there, because the Constitution limited the Federal government to only certain things and all other rights were retained by the people. It was only added as an amendment to ensure that it wasn't overlooked, as were all the other amendments.