Question: when did hemp become illegal in the us
[{'answer': '1970', 'provenance': [{'wikipedia_id': '963313', 'title': 'Hemp', 'start_paragraph_id': 85, 'start_character': 92, 'end_paragraph_id': 85, 'end_character': 96, 'bleu_score': 1.0, 'section': 'Section::::Producers.:Russia and Ukraine.\n'}]}]