If bitcoin being legalized it means that they control bitcoin so it will affect bitcoin paradigm as decentralized currency.
There is pros and cons for legalization but overall it's also keep bitcoin popularity getting increase
No one could control the bitcoin network but any government could control the flow of money going out of their country and that is how these legalization works too,they monitor the flow of money to bitcoin by controlling or keep a tab at the exchanges running in that particular country and taxing the users on the process.