Measures for the enforcement of mortmain legislation were laid down in some detail in the 1279 statute, although, as with so many aspects of the text, these too present problems. The statute appears to provide for two separate and potentially conflicting lines of action. In the event of illegal acquisition, the crown and other immediate lords, as appropriate, were to enter and take seisin within one year. Should the immediate lord not enter within this time, his right devolved on the next lord over him for the following six months. If he too neglected the opportunity, the right passed to each successive overlord up to the king. Thus far the procedure seems straightforward. However, the statute also provided that if all mesne lords had not entered within a year, the crown might enter and take the land into royal keeping pending the enfeoffment of a suitable military tenant. It is difficult to see how the rights of any mesne lord other than the immediate overlord as given in the first procedure could be reconciled with the second, nor is there much evidence as to how this apparent conflict worked out in practice.

Mesne lord intervention was evidently not a dead letter. In the time of Edward I, William Tochet entered and took possession of property in Appleby (Humberside) belonging to Thornholme Priory. His grievance was that his tenants, under cover of a lease, had alienated the holding in perpetuity to the priory without first seeking a licence.