The main purpose of this legislation, known as the "Defend our Coast Act," is to protect the outer Continental Shelf in the Mid-Atlantic Planning Area from oil and gas exploration and production. This is achieved by amending existing law to prohibit any leases for such activities in this specific area. The key provision of the Act is a clear prohibition on the issuance of leases for oil and gas exploration, development, or production in the Mid-Atlantic outer Continental Shelf.