There is no way around this. If someone remarries while his/her spouse is still alive and the marriage has not been annulled, having a sexual relationship with the new spouse (or anyone else for what matters) is adultery - and someone who not only committed adultery, but does not make sincere and honest attempt to avoid it in the future cannot receive the Holy Communion.

Marriage is either indissoluble or it isn't - and the Catholic marriage is.