From The Collaborative International Dictionary of English v.0.48 [gcide]:
Forbiddance \For*bid"dance\, n.
The act of forbidding; prohibition; command or edict against
a thing. [Obs.]
[1913 Webster]
How hast thou yield to transgress
The strict forbiddance. --Milton.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
forbiddance
n 1: an official prohibition or edict against something [syn:
ban, banning, forbiddance, forbidding]
2: the action of prohibiting or inhibiting or forbidding (or an
instance thereof); "they were restrained by a prohibition in
their charter"; "a medical inhibition of alcoholic
beverages"; "he ignored his parents' forbiddance" [syn:
prohibition, inhibition, forbiddance]