Romans 2:14-15 does not say the moral law is written on anyone's heart. What it says is that "THE WORK" of the law is written on the heart - meaning the conscience provides the same function as the law provides. It approves and disapproves of WHATEVER STANDARD of right and wrong that the conscience has been trained to accept by family, culture or religion.
That is so lame. First of all these are described as DOERS of THE law (AND THEYRE JUSTIFIED!) who do by nature the things of THE law, and, it is not A law, it is THE law as is with the rest of the context:
12 For as many as have sinned without law shall also perish without
the law: and as many as have sinned under
the law shall be judged by
the law;
13 for not the hearers of
the law are just before God, but the
doers of the law shall be justified:
14 (for when Gentiles that have not the law
do by nature the things of the law, these, not having
the law, are
the law unto themselves;
15 in that they show the work of
the law written in their hearts, their conscience bearing witness therewith, and their thoughts one with another accusing or else excusing them);
16 in the day when God shall judge the secrets of men, according to my gospel, by Jesus Christ.
17 But if thou bearest the name of a Jew, and restest upon
the law, and gloriest in God,
18 and knowest his will, and approvest the things that are excellent, being instructed out of
the law,
19 and art confident that thou thyself art a guide of the blind, a light of them that are in darkness,
20 a corrector of the foolish, a teacher of babes, having in
the law the form of knowledge and of the truth;
21 thou therefore that teachest another, teachest thou not thyself? thou that preachest a man should not steal, dost thou steal?
22 thou that sayest a man should not commit adultery, dost thou commit adultery? thou that abhorrest idols, dost thou rob temples?
23 thou who gloriest in
the law, through thy transgression of
the law dishonorest thou God?
24 For the name of God is blasphemed among the Gentiles because of you, even as it is written.
25 For circumcision indeed profiteth, if thou be a doer of
the law: but if thou be a transgressor of
the law, thy circumcision is become uncircumcision.
26 If therefore the uncircumcision keep the ordinances of
the law, shall not his uncircumcision be reckoned for circumcision?
27 and shall not the uncircumcision which is by nature, if it fulfil
the law, judge thee, who with the letter and circumcision art a transgressor of
the law?
The only heart where the law of God has been written upon is the heart of believers by the regenerating power of the Holy Spirit - 2 Cor. 3:3 as that is the specific administration of the "new" covenant.
The passage is describing the regenerate heart with the work, the essence, of both the law and the religion of Jesus Christ instilled within it - agape.
12 All things therefore
whatsoever ye would that men should do unto you, even so do ye also unto them: for this is the law and the prophets. Mt 7
8 Owe no man anything, save to love one another: for
he that loveth his neighbor hath fulfilled the law.
9 For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not covet, and if there be any other commandment, it is summed up in this word, namely, Thou shalt love thy neighbor as thyself.
10 Love worketh no ill to his neighbor: love therefore is the fulfilment of the law. Ro 13
Why you all cannot see the continuity, the synonymy of "the work of the law written in their hearts", "he is a Jew who is one inwardly" and "circumcision is that of the heart" in the context is beyond me. These are born from Jerusalem above, true Jews, the Israel of God.