Expressing Possibility


Possibility can be expressed in legislation using a variety of words and expressions. Legislative counsel should take care to use a word or an expression that is appropriate to the context, that expresses an appropriate degree of possibility, and that does not create ambiguity about the intended meaning.

Discussion and examples

Possibility can be expressed in legislation using verb forms such as can, could, may and might, and expressions that include the words possible and likely and their variants. These words and expressions should be employed judiciously, as they do not necessarily express the same kind or degree of possibility and could, in certain contexts, lead to ambiguity.


This word expresses possibility in a general sense. The same meaning is conveyed by the expression “it is possible (for X) to”:[1] 

Because can is also associated with ability, it is especially suitable in cases where “the possibility of an action is due to some skill or capability on the part of the subject referent”,[2] even if the capability is not necessarily desirable:


This word, which is the past-tense form of can, is used to express possibility in hypothetical situations and to express a weaker or more tentative possibility than can:[3]


This word also denotes possibility, but, unlike can, it is used to describe epistemic possibility, that is, possibility in the sense that the speaker does not know whether the proposition is (or may become) true. It expresses possibility associated with chance [4] rather than with capability. The same meaning is conveyed by the expression “it is possible that”:[5]

NB: In legislation may is principally used to grant powers or permission (see the article “Expressing Permission, Powers or Rights”). It is recommended that, to minimize the possibility of ambiguity, legislative counsel avoid using may in cases where more than one interpretation is possible, especially if they have already used the word in its principal legislative meaning in the provision:


This is the past-tense form of may. Like could, it can be used to express possibility in hypothetical situations:

any other element on board the vessel that might, if damaged or used illicitly, pose a risk to people, property or operations

Might can also be used to express a more tentative or weaker possibility than may. (See footnote 3.) Swan actually attempts to quantify the difference between the two words by saying that, in the statement “I may go to London tomorrow”, there is perhaps a 50% chance of the proposition becoming true, while in the statement “Joe might come with me” there is perhaps a 30% chance.[8]


This word is used frequently in legislation:

Dictionaries generally give likely a meaning similar to “probable” or “to be expected”.    A Dictionary of Modern Legal Usage places its strength between possible and probable (it points out that Glanville Williams describes likely as “a strong ‘possible’ but a weak ‘probable’”).[9] It also says that “most often it indicates a degree of probability greater than five on a scale of one to ten”, but cautions that “it may also refer to a degree of possibility that is less than five on that same scale.”[10] Legislative counsel should bear in mind that the degree of possibility or probability conveyed by this word can vary, although they are probably safe in relying on the dictionary definitions.


This word “embraces a wide gamut: everything from the remotest chance to a 100% certainty.”[11] The examples found in legislation suggest, however, that it is used most often to express possibility in the sense of “capability” (“it is possible to”) rather than “chance” (“it is possible that”):[12]