What constitutes an artificial restraint?
For classical liberals, that means being free from the constraint imposed by other individuals.
Today the definition of "restraints" is being expanded beyond the artificial to the point where everything is being declared a "human right" without any consideration for the fact that some of those things can only be provided by taking from someone else (resources and/or labor). Basically, more and more people feel that people should be free from natural restraints like the responsibility of having to provide for oneself (or at least trying to). But the rub is that the only way to free some people from those natural restraints is bondage of others to provide for them.