Canonum De Ius Positivum
Canons of Positive Law
III. Rights
3.3 Rights Suspension and Corruption
Article 104 - Easement
Canon 2101 (link)
As a person holding a mortgage never actually owns the land, only leases it, they are generally powerless to prevent the executors and administrators of the higher estate selling separate rights under lease to another party, unless they can prove the activities of the second party will grossly deprive them of fundamental rights of the operation of their tenancy.