It is about the indissolubility of marriage. "Therefore now they are not two, but one flesh. What therefore God hath joined together, let no man put asunder." (Matthew 19:6) Those who deliberately disregard God's clear directive on this matter have (by their own free will) REJECTED the "Divine Encounter".
CCC 1874 To choose deliberately - that is, both knowing it and willing it - something gravely contrary to the divine law and to the ultimate end of man is to commit a mortal sin. This destroys in us the charity without which eternal beatitude is impossible. Unrepented, it brings eternal death.
The indissolubility of marriage is not the only mandate. All of God’s commandments are mandates, not options. For sure, the re-married Catholic breaks the mandate but this does not end there. This is why we have annulments that go far back and recognizes human frailty and repentance. The attacks on Pope Francis we have recently seen on FR have degenerated into ad hominem stuff. Christ did not turn away from the much-married Samaritan woman who at the time had a live-in lover. Communion is a one-o-one Divine Encounter not some meaningless ritual or a liberal label to be applied for branding the fallen.
No they haven't...We are not under the law but under Grace, with a merciful God...We are not God's chosen people (Jews under the law) who those things were directed to, we are the Gentile church with much liberty to make those Jews jealous...