Source : Webster's Revised Unabridged Dictionary (1913)

Unlawful \Un*law"ful\, a.
   Not lawful; contrary to law. -- {Un*law"ful*ly}, adv. --
   {Un*law"ful*ness}, n.

   {Unlawful assembly}. (Law) See under {Assembly}.

Source : WordNet®

unlawfully
     adv : not conforming to the law; "they were unlawfully married"
           [ant: {legally}]