If you mean convenants or restrictions, then it is often the seller of the land who hold this. That will often mean that it is now not relevant - but the danger of disobeying a convenant is that a buyer's solicitor will find out about it when you eventually come to sell.
Sometimes a restriction is put in place because the local development control department (Planning Dept) demand it as part of granting a planning application on the land in the first place. The seller (often a developer) then copies the restriction across into the purchase contract document. For example, thou shalt not have a fence bordering the front of the property normally comes from such a source. The developer who sells you the new house couldn't give a fig about this.