This is a topical area for the courts, which have moved to imply various limitations or tests on decision makers powers and when they can be challenged. This is made more difficult for lay users and lawyers alike in that implied restrictions are (by definition) not apparent from the words of the relevant contract itself.

These limits are applied by the courts not just to fiduciaries (such as trustees or directors), but also to non-fiduciaries (eg banks and employers).

Recent case law includes:
- Pitt v Holt (SC) - trustee decisions (2013)
- Braganza (SC) - contractual discretions (2015)
- Eclairs (SC) - directors powers: proper purposes (2015)
- IBM UK Holdings v Dalgleish (CA) - employer powers under pension plans (2017)
- British Airways (CA)- pension plan - proper purposes (2018)

The book reviews the relevant doctrines of:
- Interpretation rules
- Proper purposes;
- Due consideration of relevant factors
- Full perversity (no reasonable decision maker)

This title is included in Bloomsbury Professional's Pensions Law online service.