I already consulted Is it "less than" or "lesser than"? (but the answers are contentious) and Using "lesser" or "smaller" in reference to an abstract quality. Mod RegDwight's comment under:
Lesser is an adjective. Less is an adverb. Everything else follows.
Source: p 56, The English Legal System 2012-2013, Gary Slapper
In Fitzpatrick v Sterling Housing Association Ltd (1999), the House of Lords had extended the rights of such individuals to inherit the lesser assured tenancy by including them within the deceased person’s family. It declined to allow them to inherit statutory tenancies, however, on the grounds that they could not be considered to be the wife or husband of the deceased as the Act required.
assured is an adjective. Is this why lesser is the only choice? Why not less-assured or less assured?
https://english.stackexchange.com/a/24749 says "Less refers to quantity, lesser refers to quality."
Aren't we concerned with the quantity of the 'assured tenancy' here? So why not less?