In a manner that enforces or compels; in a way that suggests force or strong authority.
From the present participle 'enforcing' plus the adverb suffix '-ly.' The construction creates an adverb that modifies how an action is performed in terms of enforcement.
This word is virtually extinct in modern English—you'll almost never hear or read it. But it shows how English allows us to create adverbs from almost any verb form, even if most people don't actually use them.
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