Question: when did it become illegal to prevent the marriage of an interracial couple in the united states
[{'answer': '1967', 'provenance': [{'wikipedia_id': '3872186', 'title': 'Interracial marriage', 'start_paragraph_id': 2, 'start_character': 146, 'end_paragraph_id': 2, 'end_character': 150, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3872186', 'title': 'Interracial marriage', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 346, 'bleu_score': 0.6804042741977431, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12811463330590484008}, 'section': 'Section::::Abstract.'}]}]