And this is why some call it liberty. You can give a slave freedom by helping them to escape, but you have not provided liberty if the slaver can just hunt down and recapture the free'ed slave.
John Locke said on the subject of liberty: "Freedom is constrained by laws in both the state of nature and political society. Freedom of nature is to be under no other restraint but the law of nature. Freedom of people under government is to be under no restraint apart from standing rules to live by that are common to everyone in the society and made by the lawmaking power established in it. Persons have a right or liberty to (1) follow their own will in all things that the law has not prohibited and (2) not be subject to the inconstant, uncertain, unknown, and arbitrary wills of others."
John Locke said on the subject of liberty: "Freedom is constrained by laws in both the state of nature and political society. Freedom of nature is to be under no other restraint but the law of nature. Freedom of people under government is to be under no restraint apart from standing rules to live by that are common to everyone in the society and made by the lawmaking power established in it. Persons have a right or liberty to (1) follow their own will in all things that the law has not prohibited and (2) not be subject to the inconstant, uncertain, unknown, and arbitrary wills of others."