In any contract, may can be used to convey two meanings. (I’m not counting the superfluous may discussed in MSCD 3.58.)
May primarily serves to convey discretion, as in The indemnified party may at its expense retain separate co-counsel.
But may can also be used to convey the possibility of something coming to pass, as in Acme may be subject to further litigation.
Using one word to convey two possible meanings violates a cardinal rule of drafting—be consistent!—and raises the spectre of ambiguity. Here’s an example from MSCD 3.56:
Take the following provision: During the term of this agreement, the Investigator may provide the Sponsor with confidential information. This could mean that the Investigator is authorized to provide the Sponsor with confidential information, but it could also mean that it is possible that the Investigator will do so.
I don’t often encounter may used to convey the second possible meaning. And one can usually discern from the context which meaning is intended. Nevertheless, I find this ambiguity annoying. MSCD suggests two ways to avoid it:
[I]f the possibility of an event coming to pass has no contractual ramifications, it might be best to omit any reference to it. If, by contrast, you need to address the consequences of that event coming to pass, it would probably be best to restructure the provision in a way that omits may. For instance, the example in 3.56 could be rephrased as If during the term of this agreement the Investigator provides the Sponsor with confidential information, then ….
Here’s an even simpler (but not necessarily better) way to avoid this ambiguity: To convey the possibility of something coming to pass, instead of may use 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 says that might “suggests a slightly lower degree of possibility” than may, but I don’t think that represents much of an obstacle to use of might. The parties are less interested in parsing the likelihood of the event happening than in specifying the parties’ rights and obligations if it does happen.
Regarding expects to, I wouldn’t want it to be construed as expressing an obligation, but I don’t see how that could happen.