Liberalization refers to laws or rules being liberalized, or relaxed, by a government. You might talk about the liberalization of marriage laws in states that allow same-sex marriage.
Liberalization came to the English language in 1835, from the word liberal. Literally translated, it means the act of making more liberal, or freer. While liberal is used to refer to more than just politics––you can have liberal parents––liberalization is used only when speaking of economic or social policies or other government regulations.