The Gemara (Sanhedrin 58a) declared that a non-Jew is liable to death for learning Torah (at least the parts not relevant to him practically). If you read the passuk תורה צוה לנו משה מורשה literally, “The Torah did Moshe command us as an inheritance,” then if a non-Jew learns Torah, he’s in violation of theft; if you expound מורשה as מאורשה, then you get “The Torah did Moshe command us as a wife,” and then the non-Jew is in violation of adultery.
In practice, what should one’s response be if and when a non-Jew approaches him asking about some area of Halacha? Should the Jew explain it to him, perhaps as simply as possible without all the esoteric details, or should he not explain it at all, politely explaining why (while not quoting the above Gemara, as that would also be teaching him Torah)?