Who was the Law given to?

It has been said that the Law what for the Jews only. But the "Jews" were not around until Judah was born.
Abraham new God's Law:
Gen 26:5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.

Adam knew HIS law:
Gen 2:3 And God blessed the seventh day, and *sanctified* it: because that in it he had rested from all his work which God created and made.
And taught his sons:
Gen 4:7 If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him.
After Seth's son was born, men began calling upon the LORD:
Gen 4:26 And to Seth, to him also there was born a son; and he called his name Enos:** then began men to call upon the name of the LORD.**

Then when the children of Israel left Egypt, they were told the strangers living among them MUST TOO follow the law:

Exo_12:49 One law shall be to him that is homeborn, and unto the stranger that sojourneth among you.
Exo_20:10 But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: