May can mean might, but I don’t think that’s any reason for me to stop recommending that you use may as the workhorse for language of discretion.
Here’s what MSCD 3.160–62 says about may meaning might:
In addition to conveying discretion, may can also be used to express that something might come to pass. The result is ambiguity. Consider the following provision: The Investigator may provide the Sponsor with confidential information. It could mean that the Investigator is authorized to provide the Sponsor with confidential information, but it could also mean that it’s possible that the Investigator will do so.
Although one can usually discern from the context which meaning is intended, it would nevertheless be best to avoid this sort of ambiguity. If the intention were to convey possibility, you could restructure the provision in question to omit may. For example, the above example could be rephrased as If the Investigator provides the sponsor with confidential information, then …
Alternatively, to convey the possibility of something coming to pass one could instead of may use either might (if it’s uncertain whether the event will come to pass) or expects to (if it’s likely that the event will come to pass and a party is the subject of the sentence). The Cambridge Grammar of the English Language, at 200, says that might “suggests a slightly lower degree of possibility” than may, but that shouldn’t be an obstacle to the use of might—the parties to a contract would be less interested in parsing the likelihood of an event happening than in specifying the parties’ rights and obligations if it does happen.
But even if you use something other than may to express the meaning might, that could leave readers wondering whether a given may in fact means might. That concern was expressed in two comments to my recent post on shall not … unless versus may … only if (here).
Here’s the relevant part of Vincent Martorana’s comment:
[A]s a general matter, “may” can mean “is/are permitted to” (i.e., discretion) or “might possibly.” I know that context plays an role here, but I now use “is/are permitted to” to convey discretion rather than “may.” And I use “might” to convey possibility.
And here, to essentially the same effect, is the relevant part of Rick Colosimo’s comment:
As for “may,” I’ve banished it in favor of “is entitled to,” with “is not entitled to” as a replacement for “may not.” I agree that the ambiguity of “has a right to” and “might do X” is not helpful.
But before jettisoning a word because it conveys alternative meanings, it’s appropriate to ask (1) what risks the alternative meanings pose and (2) what the cost is of change.
I don’t see that may-means-might creates meaningful risk. Consider again the sample sentence used in the above MSCD extract: The Investigator may provide the Sponsor with confidential information. Party A says that may expresses discretion; Party B says that may means might. It’s hard to see what benefit Party B could derive from its position—if you accept that the Investigator might provide confidential information, it’s hard to see how you could use that to argue that the Investor isn’t allowed to provide confidential information.
(By the way, the meaning might occurs in what should be language of declaration: either a party is making a statement of fact that it might do something, or a party is acknowledging that the other party might do something. That requires that you introduce the sentence with Party A states that (no, not Party A represents and warrants that!) or Party B acknowledges that. Of course, given the chaotic state of verb structures in traditional contract language, use of language of declaration doesn’t rule out the possibility that in using a given may a drafter had in mind discretion.)
As regards the cost of change, I feel as if I’m already asking people to give up a lot that’s familiar. Asking them to drop may—a basic building block of everyday English—in favor of a more cumbersome structure that offers no, or negligible, benefits seems counterproductive and perhaps quixotic.
Compare that to my preference for shall not over may not. (See MSCD 3.223–24.) The risk of ambiguity is greater, in that may not conveys three alternative meanings, not two, and those meanings (is not authorized to; might not; is authorized not to) are semantically inconsistent. And compared to the proposed replacements for may, the replacement—shall not—isn’t cumbersome, particularly when you take into account that I use shall to express obligations imposed on the subject of the sentence.
My thanks to Vincent and Rick for prompting me to think through this again.