Sentence:  According to the <WSD>doctrine of necessity</WSD>, civilization cannot exist without the rule of law. Therefore, the courts cannot tolerate a legal vacuum. The <WSD>doctrine of necessity</WSD> holds that the laws of an illegal government must be deemed to be effective to the extent that they do not violate the constitution. 
Meaning of the word marked with <WSD> tags:  The principle that the laws, of governance in action, should be deemed valid insofar as they do not contradict the constitution. Validated on the basis that maintenance of government is of greater utilitarian value than maintenance of the law.