Conditions vs Requirements

This investigation started from this phrase:

The difference between a logical condition and a requirement may be understood in terms of the (Kantian) difference between analytic statements (logical conditions) and synthetic statements (requirement). [Lehmann, J., Breuker, J., & Brouwer, B. (2004). Causation in AI and Law. Artificial Intelligence and Law, 12(4), 279–315] 

In philosophy these concepts are usually defined along these terms: analytic propositions are true by virtue of their meaning (eg. robins are birds), i.e. truth seems to be knowable by knowing the meanings of the constituent words alone; synthetic propositions are true by how their meaning relates to the world (eg. robins fly), i.e. truth is knowable by both knowing the meaning of the words and something about the world. (See Analytic/Synthetic Distinction on the Stanford Encyclopedia of Philosophy.)

However, conditions and requirements have a quite different meaning in other domains. For example, general conditions refer usually to an inherent part of an agreement. They are more static (considering a certain domain), and remain the the same from contract to contract, dealing with contractual principles. Supplements are added for a particular contract. On the other hand, general requirements cover an inherent part of the specifications of the contract: they are more dynamic because they change from contract to contract, and deal with minute specifications applicable to that particular case.

In that article the quoted phrase followed these statements:

In other words, the grounds for responsibility attribution do not have the status of logical or strictly rational conditions. They rather are widely accepted requirements, which generally grow out of tradition and that are progressively codified by legislators in the Law. [ibidem]

Integrating this, we may infer the following general rule: conditions come from (logic) necessity, requirements come from use. Considering the examples given above, we may explain the different uses in this way: 

• general conditions adhere necessarly to the current legal dispositions, while the description of the general requirements is a result of the expertises of the provider and user, 
• grounds for responsibility grow up with the legal production, so they are requirements,
• analythic propositions are logically necessary, while synthetic propositions result from our experience.

Conditions in Law

From West's Encyclopedia of American Law:

A condition may be either express or implied.

• An express condition is clearly stated and embodied in specific, definite terms in a contract, lease, or deed, such as the provision in an installment credit contract that, if the balance is paid before a certain date, the debtor's interest will be reduced.
• An implied condition is presumed by law based upon the nature of a particular transaction and what would be reasonable to do if a particular event occurred. If a woman leases a hall for a wedding on a certain date, her ability to use the hall is based on its implied continued existence. If the hall burns down before that date, use of the hall is impossible due to fire; therefore, the law would imply a condition excusing the lessor from liability. 

In the law of contracts, as well as estates and conveyancing, conditions precedent and subsequent may exist.

• A condition precedent must occur before a right accrues. A woman may convey her house to her son based on the condition that the son marry by the age of twenty-five. If the son fails to marry by that age, he has lost his right to the house. Similarly, in contract law, if an agreement is signed by one party and sent to a second party with the intention that it will not become enforceable until the second party signs it, the second party's signature would be a condition precedent to its effectiveness. 
• A condition subsequent means that a right may be taken away from someone upon the occurrence of a specified event. An owner of property may convey land to a town on the condition that it be used only for church purposes. If the land conveyed is used to build a shopping mall, then ownership would revert to the original owner. A condition subsequent may also affect a transaction involving a gift. In many states, an engagement ring is regarded as an inter vivos gift to which no conditions are attached. In some states, however, its ownership is considered to be conditioned upon the subsequent marriage of the couple involved; therefore, if a woman does not marry the man who gave her the engagement ring, ownership reverts to him and she must return it to him. 
• Concurrent conditions are conditions in the law of contracts that each party to the contract must simultaneously perform.