Local authorities are prevented from reserving contracts by geographical location by section 17(5)(e) Local Government Act 1988.
16.3 O dan Reoliadau Cynllunio Gwlad a Thref (Rheoli Hysbysebion) 1992, mae'n drosedd arddangos hysbyseb awyr agored heb gael caniatâd yr awdurdod cynllunio lleol.