Fear of the law, to begin with has to be instilled in people. What has worked for ages, will work now, no amount of modernity or practicality can substitute illegallity and immorality.
Yes, there is scope for abuse. Just like a knife can be used by a surgeon to save lives, it can be used by a murderer to end lives . Tools will always have to exist , you cannot wish away tools because their is a potential for immorals to misuse it. If you think you can get rid of your wife that way, shame on you. And may the wrath of the Law and God be on you. So a lot depends on the State's willingness to put morality as the canon of the society. There are many connected things here like polity, type of government, religious tones of society etc. however, none can override the fact that what is wrong will always be wrong.