law vs put behind bars

law is a noun but put behind bars is not a noun.

Word	Noun	Adjective	Verb	Adverb
law	Yes	No	No	No
put behind bars	No	No	Yes	No

law (noun)	put behind bars (noun)
the learned profession that is mastered by graduate study in a law school and that is responsible for the judicial system
a rule or body of rules of conduct inherent in human nature and essential to or binding upon human society
a generalization that describes recurring facts or events in nature
the branch of philosophy concerned with the law and the principles that lead courts to make the decisions they do
legal document setting forth rules governing a particular kind of activity
the collection of rules imposed by authority
the force of policemen and officers

law (verb)	put behind bars (verb)
	lock up or confine, in or as in a jail