David Bernstein of The Volokh Conspiracy writes:
I frequently have disputes with law reviewer editors over the use of dashes. Unlike co-conspirator Eugene, I’m not a grammatical expert, or even someone who has much of an interest in the subject.
But I do feel strongly that I shouldn’t use a dash between words that constitute a phrase, as in “hired gun problem”, “forensic science system”, or “toxic tort litigation.” Law review editors seem to want to generally want to change these to “hired-gun problem”, “forensic-science system”, and “toxic-tort litigation.” My view is that “hired” doesn’t modify “gun”; rather “hired gun” is a self-contained phrase. The same with “forensic science” and “toxic tort.”
Most of the commenters (thus far) are right in advising Bernstein that the “dashes” — he means hyphens — are necessary. Why? To avoid confusion as to what is modifying the noun “problem.”
In “hired gun,” for example, “hired” (adjective) modifies “gun” (noun, meaning “gunslinger” or the like). But in “hired-gun problem,” “hired-gun” is a compound adjective which requires both of its parts to modify “problem.” It is not a “hired problem” or a “gun problem,” it is a “hired-gun problem.” The function of the hyphen is to indicate that “hired” and “gun,” taken separately, are meaningless as modifiers of “problem,” that is, to ensure that the meaning of the adjective-noun phrase is not misread.
A hyphen isn’t always necessary in such instances. But the consistent use of the hyphen in such instances avoids confusion and the possibility of misinterpretation.
The consistent use of the hyphen to form a compound adjective has a counterpart in the consistent use of the serial comma, which is the comma that precedes the last item in a list of three or more items (e.g., the red, white, and blue). Newspapers (among other sinners) eschew the serial comma for reasons too arcane to pursue here. Thoughtful counselors advise its use. Why? Because the serial comma, like the hyphen in a compound adjective, averts ambiguity. It isn’t always necessary, but if it is used consistently, ambiguity can be avoided. (Here’s a great example, from the Wikipedia article linked in the first sentence of this paragraph: “To my parents, Ayn Rand and God.” The writer means, of course, “To my parents, Ayn Rand, and God.”)
This all reminds me of the unfortunate demise of the comma in adjectival phrases. If “hired” and “gun” were meant to modify “problem” separately, the expression would (should) be written “hired, gun problem.” Not that “hired, gun problem” means anything, but if it did, the proper use of a comma between “hired” and “gun” would ensure against misreading the phrase as “hired gun problem” (unpunctuated, as Bernstein prefers) as “hire-gun problem.”
A little punctuation goes a long way.