Sforno on Leviticus 24:15/ספורנו על ויקרא כ״ד:ט״ו

1כי יקלל אלוקיו, and thereby transgresses the negative commandment אלוקים לא תקלל, (Exodus 22,27)

2ונשא עונו, he will have to carry the burden of his punishment. In other words, this is a problem between him and his Maker, no human court being involved, seeing the sin was committed in private and he had not cursed G’d’s essence but one or more of His attributes. This “leaving him to G’d,” is also applicable when the blasphemer “only” cursed one of the attributes G’d is known by.