A legal doctrine derived from the implied covenant of good faith and fair dealing, and often codified in state commercial landlord-tenant statutes, which prohibits a landlord from arbitrarily or capriciously withholding consent to a proposed commercial sublease when the primary lease requires such consent but does not grant the landlord sole discretion. The landlord's decision must be based on objectively reasonable, commercially relevant criteria related to the subtenant's financial viability, business use, or potential impact on the property, not on personal preference, desire to re-lease the space directly, or unrelated animus.