It was written as an assurance, the constitution doesnt GIVE the fed the power to regulate speech, religion or guns. Nor does it give them the power to quarter soldiers nor implement arbritrary search and seizure nor administer cruel and unusual punishment.
The BOR is an incomplete listing, and could be shortened to amendment 10.
Fed has no powers other than granted by the Constitution. BOR is superfluous, do a net search on the preamble to the BOR (which has been removed from nearly every copy of Constitution -- it reads in part:
THE Conventions of a number of the States having at the time of their adopting the Constitution, expressed a desire, in order to prevent misconstruction or abuse of its powers, that further declaratory and restrictive clauses should be added: And as extending the ground of public confidence in the Government, will best insure the beneficent ends of its institution
The bold indicates that, EVEN absent the BOR, any action that violated the 'rights' in the BOR, would be a misconstruction and abuse of power.
Read the restrictions on state power in the 14th, Sec 1.