It’s June 30th, 1926, and a police officer is hitting someone over the head with a club. This was, in 1926, apparently considered a normal enough occupational activity that a newspaper cartoonist could reference it as something cops had recently been told to stop doing, rather than, say, something that had always been illegal.
That's the world this cartoon strip lives in, so keep that in mind.

Panel by panel
Panel one. A police officer is depicted mid-thump, doing what the caption calls "a copper's big way to diversion." He's been ordered to stop. "Orders am orders," the caption notes, with a shrug so audible you can almost hear it. The implication is that roughing people up was, until very recently, just something cops did when they got bored.

Panel two. Smashing in doors is also out this season. The cartoon allows that "the door might have led to a bootlegger's place, but we all know better." This is a Prohibition-era joke with a lot of weight behind it. By 1926, everyone knew that some of the door-smashing happening in the name of the Volstead Act was a little more enthusiastic than the law strictly required. The cartoonist is winking at something the whole country understood. Although I’ve seen plenty of “Wets declare war this summer” headlines to know this was still very much a thing. Maybe it was just federalized and not so much local beat cops anymore.

Panel three. The cop can no longer flirt with women on his beat either. "Sweetie's been told to beat it," the caption reads. "Hard on the pavement pounders." Whether this was a new department policy or just the general mood of reformers cracking down on police behavior in 1926 is unclear from this strip alone, but the joke is that it's one more pleasure confiscated. I’ve seen this one enough to know it very much was a thing cops did regularly.

Panel four. The cop sits alone with the question the strip has been building to: "What can a cop do? Poor boy. Gotta have some fun. Let's see if there isn't some way to stir up trouble without working too hard at it."

Panel five. The answer arrives. "Pick on the motorists. Tag their parked boats. It's certainly a cinch, and gosh, it's a soft job."

The parking ticket, in its natural habitat.
Why this exists
The car was still relatively new in 1926, and the rules around where you could park one were still being figured out in most American cities. What the cartoonist is lampooning isn't really the parking ticket itself so much as the idea that writing them was the laziest, safest, most conflict-free thing a cop could possibly do with his time. Kind of like speeding tickets of today since parking tickets are becoming automated.
The joke is about institutional cowardice dressed up as enforcement. A cop who used to smash bootleggers' doors in now walks down the street chalking tires.
Whoever drew this understood that the parking ticket wasn't just an administrative nuisance — it was a symbol of a police department finding the path of least resistance after being told, one by one, to stop doing all the things it used to do instead.
One hundred years later the complaint is identical. The cartoon has barely aged.
