smuggled goods; contraband
Refers to items illegally traded or transported, often across borders or in violation of regulations.
Smuggled goods were seized at customs.
He was arrested for dealing in contraband.
禁制品 are prohibited goods in general, often by law or regulation, whereas 密売品 emphasizes the act of illegal selling.
Compound of 密売 (illegal selling) + 品 (goods). The exact historical derivation is uncertain, but the meaning is transparent from its components.