Actually there is no clause in the Constituation about common defense, that is just briefly mentioned in the preamble.
{...
We the people of the United States, in order to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this Constitution for the United States of America.
...}
I would not say the preamble could be used in a court of law in order to justify something.
I have read our Constitution.
Here are the general powers delegated to Congress:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises,
to pay the Debts and provide for the common Defence and general Welfare of the United States;
but all Duties, Imposts and Excises shall be uniform throughout the United States;
I see, the term "gerneral" does not need to be a quote but a description of generic duties and means.
Although whenever I get into a constitutional discussion, it always hits me that the federal War on Drugs, federal gun control, executive undeclared wars, etc., are totally illegal.
yet, the right wing prefers to blame the Poor instead of abolish non-express powers.
What used to be the difference between the right and left constantly changes.
For example, gun control was created by the right, in order to allow vigilantes like the KKK to more easily murder and intimidate Blacks, immigrants, and labor organizers.
Why the left now supports gun control, I have no idea?
It makes no sense at all, since it means going back to the days of leaders like Dr. MLK Jr. being murdered.
The right used to be fiscally conservative over things like balances budgets and staying out of foreign wars.
But then the right started to use federal spending on the Industrial Military Complex as an open pork barrel.
And we come full circle again, where Hillary was supporting the illegal use of force for regime change in Iraq, Afghanistan, Libya, Panama, Egypt, Syria, etc.
I prefer going back to more local control, because then it is harder for government to do things that are wrong without even bothering to make any sort of justification. We should end all federal actions that harm people, like the war on drugs, gun control, and the use of military force without congressional approval. States can deal with drugs much better, guns should vary from state to state, and state representatives would have exposed the lack of evidence for WMD in Iraq and prevented the useless war.