Vertical restraints are competition restrictions in agreements between firms or individuals at different levels of the production and distribution process.
Vertical restraints can take numerous forms, ranging from a requirement that dealers accept returns of a manufacturer's product, to resale price maintenance agreements setting the minimum or maximum price that dealers can charge for the manufacturer's product.
Section 1 of the Sherman Antitrust Act governs all the vertical restraints involving interstate commerce in the United States.
Section 3 of the Clayton Act governs interbrand restraints involving the sale of "goods".
An "English clause" is a vertical restraint under competition law, and can be expected to have the same effect as a single branding obligation, especially when the buyer has to reveal who makes the better offer.