tl;dr: <https://www.judiciary.uk/wp-content/uploads/JCO/Documents/Ju...> (wiki overview <https://en.wikipedia.org/wiki/Twitter_joke_trial#cite_ref-Hi...>), which summarizes the very different first-instance trial (in England & Wales) of Chambers from this first-instance trial of Epstein (in Canada). In particular, Chambers was accused of threatening to blow up an airport, which is rather different than giving someone a finger. The finger was meant seriously, whereas the "threat" was clearly not meant seriously, and the conviction of Chambers is widely considered a miscarriage of justice that was only belatedly corrected. I am fairly sure that to the extent the Canadian acquittal becomes widely know, it will be considered a correct and just outcome.

The UK has at least three different criminal jurisdictions. The most readily comparable one is that of England & Wales ("E&W"). Most criminal law in modern times flows from legislation in the various parliaments based at Westminster in London ("Westminster" for short), however in Scotland and Northern Ireland there is law that is variously old enough to predate Westminster's legislative control; there is also old law in England and Wales together and separately; and finally there is new law legislated by the devolved assemblies in Wales, Scotland and Northern Ireland.

In terms of criminal law, there has been a sort of quasi-federalism in the UK and its predecessor kingdoms for centuries.

In Canada there is only one criminal law, and it is exclusively controlled by the federal parliament.

In England & Wales the criminal law is generally not codified; one finds criminal offences were (and continue to be) created in topical legislation, for instance there are new criminal offences throughout the Landlord Tenant Act, 1985, a topical act rebalancing landlord-tenant responsibilities and liabilities. In Chambers, the topical Communications Act, 2003, created the relevant criminal offence.

The Criminal Code of Canada is (practically) the only place where criminal offences can be itemized, and the creation of new offences require an amendment to the Criminal Code. These amendments are usually done in standalone Acts of Parliament, however from time to time a topical Act may amend the Criminal Code. When that happens, the Code is where one looks to understand the criminal law, not the Act which amended it.

The Code is meant to be uniformly applied and interpreted in every province and territory. However, as in most systems in which criminal law is codified, the code is not especially verbose nor exhaustive of possibilites (the law is not a computer program), and first-instance courts (and appellate courts) can resolve a prosecution with a particular set of facts differently from one another. Sometimes differences in the highest appellate courts in provinces are dealt with by modifications to the Criminal Code by the federal parliament; sometimes the matters are resolved by the Supreme Court of Canada; sometimes the differents are just left different, and typically those are situations which will require such unusual circumstances that they will never be comparable to prosecutions (for the same criminal code offence) brought elsewhere in Canada.

In Epstein the judgment makes reference to various paragraphs of the Criminal Code. The Court did not see the need to make explicit reference to paragraphs in the Charter of Rights and Freedoms, which is part of the Canadian constitution.

In Chambers the judgment makes explicit reference to the (UK) Human Rights Act, 1998, ("UKHRA") and articles of the European Convention on Human Rights (which UKHRA imported into the laws of England & Wales, Scotland, Northern Ireland, etc.). It also looks to other sources of law to consider what was meant by the wording of the Communications Act, by referenes to other legislation (e.g. the Malicious Communications Act, 1988) and case law (DPP v Collins (2006)).

Epstein was acquitted at trial. Chambers was convicted, but ultimately the High Court (in the chain of appeals against the initial conviction) quashed the conviction.

The judgments share some features, namely the use of long numbered paragraphs, and a detailed itemization of the law and evidence considered by the two Courts. Some court systems using codified criminal law tend to have very short judgments, and an acquittal might be memoralized in a single short paragraph which might take the form of, "the conditions for the conviction of the accused were not met so he is not convicted". This is fairly common in systems which descend from 19th century French law (Québec is not an example; it lost legal ties to France before then) or which have been highly influenced by it in the 20th and 21st centuries.

Finally, King Charles III of Canada is not really involved in matters of Canadian criminal law. The Constitution of Canada obliges him to delegate legislative, executive, prosecutorial, and judicial authority to Canadian institutions. The (less consolidated but very much written) constitution of the United Kingdom likewise ousts its monarch from a significant role in shaping and enforcing the criminal laws in the various UK jurisdictions; those powers are exercised by Parliament (or the national legislatures), various executive bodies and various courts.
Nobody would take the expression "King Charles III's Justice" seriously in either country, although in some contexts one would hear pretty much exactly that formalism being uttered as an essentially empty tradition.