Pluralising Noun + Noun compound ["date butoir"]

[Jean Dervin]

"Date butoir":  hyphen or no hyphen?  And is the plural "dates butoirs" to be preferred to "dates butoir"?  A correspondent (French) has just emailed me mentioning "de dates-butoir assez serrées".

[Grégory]

No hyphen and plural is dateS butoirS

About plural of compound nouns :

-when noun+noun, adjective+adjective, noun+adjective : an S for BOTH terms

-when noun+prep+noun : an S only for the first noun (des arcs-en-ciel, des chefs-d'oeuvre)

-when verb+noun , noun+verb, adverb+noun : an S only for the noun (des porte-monnaies/portemonnaies, des avant-premières,)

-when verb+verb : no S (des laissez-passer, des savoir-faire)

Unfortunately there are some exceptions... 

[Jean Dervin]

Yes - I am aware of the usual "rules".  You are very categorical in your statement about "date butoir".  Am I to assume that the French lawyer whom I quoted got it wrong?  Or would it be perhaps better to conclude that there are legitimate alternatives.

[George Hunt]

I found this :

"Le pluriel dates butoir est également rencontré, mais moins fréquemment"

http://fr.wiktionary.org/wiki/date_butoir

[Grégory]

Nobody has asked you to assume something about someone so I don't heed your remark. I just told the standard form of plurial. If you think in advance that it would be highly unlikely for a lawyer to be wrong about legal jargon then you already have your own answer to your question.   

[Jean Dervin]

No.  My question was which is to be preferred, not which is "correct".  While I don't consider "date butoir" to be legal jargon, it seemed unlikely to me (though not impossible) that a French lawyer would make a grammatical error of the kind implied by your answer.

[Vedas]

Hello,

No need to be categorical indeed.

The apposition is an English influence and it is sometimes difficult to determine the function of the words, it may be opened to interpretation sometimes.

ex: des tenues-sport, des vitesses limite, un service clients....

The general rule is to agree the two nouns as it was mentioned above when the second noun plays the function of an adjective  but what happens if all the dates have  the same deadline?

we could certainly write "des dates butoir" (before the end of a month for instance) just like in "2 vis butoir" because all the elements forms a single "butoir".

[Neil Coffey]

Try translating contracts for a living and you'll soon stop taking lawyers as an authority on the placement of hyphens and plurals... :)

[Vedas]

:) let's just try not to be as stiff as they are!

Also most often than not clerks or secretaries write the texts...which doesn't mean that lawyers are better at spelling.

[Jean Dervin]

Just for the record, the email was written personally by a friend, who happens (like me) to be a lawyer.  We are both also qualified legal translators, as it happens, though it's many years since I have acted in this capacity.

It is difficult sometimes on this forum to know or guess the level of knowledge of French of people who ask questions and therefore to pitch responses appropriately.  I wouldn't like Grégory to feel that his answer was not pertinent.  I should have been clearer in what I was asking.