How are the courts able to balance the protection of civil liberties and the protection of the common good?

The United States was born into war with the Declaration of Independence, the most important statement of liberty and natural rights ever made. Since then, America has been the world’s freest country and has become its most secure, with a military equal to any threat. America has avoided the fate of nations that have traded freedoms for promises of security, or security for unlimited freedom, and achieved neither. Yet the healthy fear that one or the other will disappear has been present in every era since the Founding.

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.