Whether to Use Language of Discretion or Language of Prohibition to Express an Action that Is Subject to Consent

The following sentences express the same meaning:

If it receives Acme’s prior written consent, the Vendor may cause one or more subcontractors to perform Services.

Unless it receives Acme’s prior written consent, the Vendor shall not cause any subcontractors to perform Services.

Which would you be inclined to use? Would your answer vary depending on which party you represent?

About the author

Ken Adams is the leading authority on how to say clearly whatever you want to say in a contract. He’s author of A Manual of Style for Contract Drafting, and he offers online and in-person training around the world. He’s also chief content officer of LegalSifter, Inc., a company that combines artificial intelligence and expertise to assist with review of contracts.