Let us be very clear here - Paul in Rom 2:14-15 is discussing the "Law", namely the Torah given to the Jews more than 3000 years earlier. It is obvious that non-Jews were (generally speaking) ignorant of stipulations of the Torah containing the Israelite covenant.
The passage in Rom 2:14, 15 is significant for other reasons - it says that non-Jews are given the law in an instinctive way and thus "are a law to themselves, even though they do not have the law. So they show that the work of the law is written on their hearts, their consciences also bearing witness, and their thoughts either accusing or defending them".
Thus, it appears that the Holy Spirit is active on the hearts or consciences of all people, even those that do not have the Torah. This is not surprising as the Israelite covenant was not the first to be given to mankind - there were earlier covenant laws given as well such as:
Edenic Covenant: Gen 1:26, 28-30, 2:16, 17.
This covenant is not as explicit as those which follow because the word “covenant” is not used. However, following the general principle that laws are never given without a being in the context of a covenant, there appears to be a clear implication of one. This covenant consists of:
- God blessed mankind, Gen 1:28
- God gives the gift of all seed-bearing plants as food, including fruit trees and green plants, Gen 1:28, 2:16
- Instruction to “be fruitful and multiply and fill the earth”, Gen 1:28
- Instruction to “subdue the earth”, Gen 1:28
- Instruction to “rule over the all creatures”, Gen 1:26, 28
- Instruction to not eat of the tree of the knowledge of good and evil else they would die, Gen 2:17. This was fulfilled in Gen 3.
Noahide Covenant: Gen 8:20 – 9:17.
The Noahide Covenant is actually a covenant with all living creatures and all mankind. It consisted of:
- This covenant was initiated in order to ensure continuity of seasons without interruption, Gen 8:21, 22.
- God promises never to curse the ground again, Gen 8:21.
- God promises never to destroy humans and animals by flood again, Gen 8:21, 9:11.
- God promises that seasons would never be stopped again, Gen 8:22.
- God commands humans to multiply and increase on the earth, Gen 9:2, 7.
- God commands humans to take charge of the earth and maintain it responsibly, Gen 9:2, 3; see also Gen 1:28, 29.
- God commands humans not to eat blood, Gen 9:4.
- God commands humans not to commit murder else an accounting will be required. Murder destroys the image of God in mankind, Gen 9:5, 6.
- The rainbow is given as a token/sign (Heb: “oth”, Gen 9:12, 13, 17) of God’s promise to save mankind.
- The covenant was initiated and solemnized by animal sacrifice, Gen 8:20.
Note that in this statement of God’s covenant of grace, it is universal and applying to all mankind and all animals (Gen 9:8-10, 16, 17), despite the recognition that mankind is evil (Gen 8:21). Further, the prohibition against murder and eating blood are specifically prohibited to prevent God’s image in mankind being marred. One of the unusual aspects of this covenant is the animals – God promises something to animals!
Thus, even without the moral framework provided by the Torah, there were other moral requirements for all mankind given before Sinai.