Kirchhoff's second law is based on the law of conservation of

Kirchhoff's second law is based on the law of conservation of energy.

According to Kirchhoff's second law, overall sum of all voltages around a closed loop in any circuit must is 0. 

This is yet another effect of both charge and energy conservation. It can be also be given as "A closed circuit loop's net electromotive force is equal to the total of its potential drops."