What is popular sovereignty?

Popular sovereignty, also called squatter sovereignty, in U.S. history, a controversial political doctrine according to which the people of federal territories should decide for themselves whether their territories would enter the Union as free or slave states.

Explanation:

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.