A more thorough explanation:

A transitory treaty is an agreement between two or more nations or sovereigns that is carried out once and for all, so that it is complete when the act has been performed. This type of treaty is different from a permanent treaty, which contemplates ongoing performance.

For example, a treaty of cession, which is a transitory treaty, involves the transfer of territory from one country to another. Once the transfer is complete, the treaty is fulfilled and no further action is required. In contrast, a treaty of alliance, which is a permanent treaty, establishes ongoing mutual and reciprocal support obligations between the parties.

Another example of a transitory treaty is a commercial treaty, which is a bilateral or multilateral treaty concerning trade or other mercantile activities. Such a treaty may be general in nature, as by supplying the framework of long-term commercial relations, or it may be specific, as by detailing the conditions of particular branches of trade or other commercial transactions.