compulsory law vs exaction

compulsory law

exaction

noun
  • The act of demanding with authority, and compelling to pay or yield; compulsion to give or furnish; a levying by force 

  • extortion. 

  • That which is exacted; a severe tribute; a fee, reward, or contribution, demanded or levied with severity or injustice. 

How often have the words compulsory law and exaction occurred in a corpus of books? (source: Google Ngram Viewer )