The word per, in the phrase "per judicium parium suorum," of
course means precisely what it does in the next phrase, "per legem
terrae;" where it obviously means according to, and not by, as it is
usually translated. There would be no sense in saying that the king
might proceed against a man by force or arms, by the law of the
land; but there is sense in saying that he may proceed against him,
by force or arms, according to the law of the land; because the
king would then be acting only as an executive officer, carrying
the law of the land into execution. Indeed, the true meaning of the
word by, as used in similar cases now, always is according to; as,
for example, when we say a thing was done by the government, or
by the executive, by law, we mean only that it was done by them
according to law; that is, that they merely executed the law.

Or, if we say that the word by signifies by authority of, the result
will still be the same; for nothing can be done by authority of law,
except what the law itself authorizes or directs to be done; that is,
nothing can be done by authority of law, except simply to carry the
law itself into execution. So nothing could be done by authority of
the sentence of the peers, or by authority of "the law of the land,"
except what the sentence of the peers, or the law of the land,
themselves authorized or directed to be done; nothing, in short, but
to carry the setence of the peers, or the law of the land, themselves
into execution.

Doing a thing by law, or according to law, is only carrying the law
into execution. And punishing a man by, or according to, the
sentence or judgment of his peers, is only carrying that sentence or
judgment into execution.