He claims to that he follows the Magna Carta as being bearing on him and of the common law.
As I understand it generally speaking, the Magna Carta came about because of the people having issue with what the King was doing or not doing. To which they together as a group drafted the document which they thought would address the problems that they feel existed in their society. They brought this document to the King, and said they wanted it to be enforced by him as a law. With some persuasion he agreed

Whatever you decide is the method of enforcing the law, common or civil, doesn't change that it was a law by the people for the good of the people. The people agree to give up certain personal freedoms in exchange for certainty of understanding between each of them and the King. Essentially they wanted it brought forth from this day forward that everyone shall drive on the right hand side of the road (or in their case left).
Now do you think every person in the society was involved in the drafting of the Magna Carta? Do you think everyone's concerns were addressed in it? Do you think every single person agreed with every single clause of the Magna Carta? Obviously not, but clearly a large portion agree there was a problem and at some point assigned someone the task of prepare a draft of what turned out to be the Magna Carta.
The point is, if Mr.Fearns thinks the Magna Carta is somehow superior to any of the laws we have in place today, then he is forgetting how the Magna Carta came to be. The fact that all the laws we have in place today were developed in the same way as the Magna Carta was. They were developed because the people thought there was a need and then brought that need forward to the legislature for consideration. The legislature being considered the will of the people (because they are the representatives of the people) then reviews the drafts; considers the need; discusses and makes possible amendments; decides in the end whether THEY think it should be brought forward as a law; then brings it to the King for adoption. In the Magna Carta they maybe had a knife to the Kings throat, in our case it is pretty much a rubber stamp by the governor general. The laws we have in place today are simply the extension of clarification on the Magna Carta that the people have asked for.
Mr.Fearns would like to erase all the advances in societies rules and go back to the basic Magna Carta. I think if he actually understood what he was giving up he would think twice about what he claims. Imagine how he would feel if one of his loved ones died because two cars collided at an intersection of two roads. There is nothing about stop signs and a requirement to obey them in the Magna Carta!
I believe it used to be lawful to beat your wife with a willow branch, as long as it was no thicker than your index finger (or something like that). Or that the punishment for cattle rustling was death. Or high treason may have been considered any act against the rule of the King and likewise punishable by death. Would attacking the King's rule not bring about a claim of treason?
Mr.Fearn's is free to find a society that my function based only on the ancient principals of the Magna Carta. Maybe there is one buried deep in the amazon jungle or somewhere in middle Africa. I can imagine there are tribes that function in a way similar to how the Magna Carta function (no roads, chief decides all conflict exclusively, health care consists of rubbing mud on the soles of ones feet, women are property of the man). But as it stands THIS society, and the lands that it occupies, operate on the laws that have been enacted by it.
Carl