why is it necessary to pass a law that allows people to exercise a right.
Easy:
Because the Congress become corrupted with Progressivism over the last 100 years.
Because the Courts have been corrupted with Progressivism over the last 100 years.
Because federalism and the checks and balances in the Constitutional system give us the State government’s power as a way to check the federal power.
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why is it necessary to pass a law that allows people to exercise a right...
Because that is a Foundation principle of practicing liberalism and participating in the democrat party.