There is absolutely no reason to strike or use violence towards your child, ever. There has been plenty of research that shows that it only leads to children that are more prone to violence.
You always get arguments that spanking should be allowed as you need to teach children respect. But then you don't understand the difference between respect and fear.
Bear in mind that in Sweden using physical punishment had been illegal since 1979 with absolutely no negative effects whatsoever. As of today, 31 countries have laws against using physical punishment.
The answer to if parents or indeed *anyone* should be legally allowed to spank their children is a clear and loud "No".