I kind of understand that point you're making, Merry Mouse. But Canon Law may be amended and, if it results in an unjust or illogical conclusion (under what many would term "natural law"), then I'd argue it should be amended.
From what Mathanxiety has explained, if I were drafting the Canon Law rule myself, it seems it would look something like this:
A person (A) who was baptised as a Catholic, and has subsequently been married in a non-Catholic ceremony (such marriage being referred to as the Previous Marriage) may be married in the Catholic Church if A failed to seek permission from the Catholic Church to celebrate the Previous Marriage. That lack of permission renders the Previous Marriage invalid.
In my view, in Johnson's case (and perhaps in many others) that's resulted in an illogical conclusion, especially for a Christian faith that claims to be the One True Church in following the teachings of Jesus Christ.
It really makes sense to return to the teachings of Christ himself. The following passage from Mark 10 lies at the centre of Christian teaching on marriage and divorce:
1He left that place and went to the region of Judea and beyond the Jordan. And crowds again gathered around him; and, as was his custom, he again taught them. 2 Some Pharisees came, and to test him they asked, "Is it lawful for a man to divorce his wife?" 3 He answered them, "What did Moses command you?" 4 They said, "Moses allowed a man to write a certificate of dismissal and to divorce her." 5 But Jesus said to them, "Because of your hardness of heart he wrote this commandment for you. 6 But from the beginning of creation, "God made them male and female.' 7 "For this reason a man shall leave his father and mother and be joined to his wife, 8 and the two shall become one flesh.' So they are no longer two, but one flesh. 9 Therefore what God has joined together, let no one separate." 10 Then in the house the disciples asked him again about this matter. 11 He said to them, "Whoever divorces his wife and marries another commits adultery against her; 12 and if she divorces her husband and marries another, she commits adultery.
This requirement for permission bit is really just complicated human rule overlay on Christ's relatively simple teaching. Christ himself criticised the Pharisees for this kind of stuff; pointless, complicated religious rules.
So, yes - I expect Canon law to be amended to a simple rule (which clearly heaps of people thought was the rule in the first place) that you may not be married in a Catholic church if you have previously been divorced. If that's the case, just make it so.
But, to be honest, the arbitrary decision-making, the arrogance, the swathes of doctrine with which I just don't agree - makes more sense for me to leave the Church because I'm guessing it isn't going to change. But I can't even fully do that, it seems, because (as mentioned above) the Church considers you a member even if you don't want to be any more!