legalization
US /ˌliː.ɡəl.əˈzeɪ.ʃən/
UK /ˌliː.ɡəl.əˈzeɪ.ʃən/

1.
the act or process of making something that was previously illegal permissible by law
:
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The legalization of cannabis has been a controversial topic.
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They are pushing for the legalization of same-sex marriage.