Intermarriage and ramifications

[Director Michael]

Hi there, I would be grateful if the Rabbi could advise how a Noahide should react to situations where a Jew is dating or in established relations with a non-Jew i.e male/female.

As badly as you may rightfully feel when you learn that this transgression is taking place, as a Gentile, there are two things to remember at the outset:

(1) It will be a noble deed and a great merit for you if you can directly or indirectly apply influence that will bring the couple to discontinue their forbidden intimate relationship - on account of their recognition of the fact that it is intrinsically forbidden. Nevertheless, you won't be liable to punishment from G-d if you choose not to do anything about it, because a Gentile is not obligated to risk incurring harm upon himself, nor even to just go out of his way, to stop a Jew or another Gentile from sinning. (However, it is not permitted for a Gentile to actively help another person commit a sin. On the other hand, a Jew is obligated and held responsible to try to persuade  another Jew to stop sinning, if possible.)

(2) It is possible and probably likely that one or both of the partners in the forbidden relationship are sinning inadvertently, because they don't know about the prohibition, or they don't know how serious it is, or they don't know that it always remains in effect.

For instance someone from his circle of friends/associates introduces him to his new Jewish girlfriend.

The best way to proceed can depend on the case-by-case details of the situation:
a) It is better to intervene as early as possible, before the couple gets very deeply into their relationship.
b) Since the explicit Torah prohibition is stated for the Jew, it is better to start by at trying to speak privately, gently and sincerely to the Jewish person, keeping in mind that words spoken from your heart will surely penetrate into the other person's heart. Even if you aren't successful in the short term, a seed will have been planted.
c) It is always good to get expert advice before acting, and in this area the expert will be an Orthodox Rabbi, and you may find one who will volunteer to become personally involved in the case. Therefore you should try to find a local Orthodox Rabbi, and we recommend using the network through Chabad.org:
https://chabad.org/centers/default_cdo/j...enters.htm

I would think it would definitely be inappropriate for a gentile to serve as an official witness, best man, bridesmaid or to even attend a wedding between such a couple as it would appear to be condoning it.

Correct.

However how far does the moral obligation extend to warning the parties involved that it would be inappropriate.

Please see the above response about this.

Should the Noahide rather ask a Rabbi to reach out to the Jewish man/woman or their parents instead?

An Orthodox Rabbi should be consulted to help arrive at the best plan of action.