Golden age young adult series with political shenanigans in space!

Question

I'm looking for a book I read in grade school in the late 70s or early 80s. I'm pretty sure it was several decades old already and one of a longer series: a golden age sci-fi version of Tom Swift or the Hardy Boys. The feel was flying cars and interplanetary navigation by slide-rule.

The entire story takes place within the solar system, with antagonists from former colonies on nearby stars.

The storyline is about a Cold War plot by the Alpha Centarians (or Sirius? Some nearish star colony) to create a spy base in the solar system on Jupiter, and Our Hero is the Science Police agent assigned to kicking them out. He does so via cleverness and a legal-political battle rather than militarily:

Our Hero takes the Centarian argument that that the Terrans hadn't colonized Jupiter and so didn't have a claim in it one step farther - he sets up a friend in a colony on one of Jupiter's moons and when the Centarians shut down that colony as infringing on their Jupiter colony he turns the argument on them: by the same logic, the Jupiter colony infringes on Terra's claim to Sol. This sways the interplanetary science court to declare that Terra has claim to the entire Solar system and that the system can't be subdivided to ridiculous levels and squabbles over each asteroid and meteor.

Answer 1

This sounds like Asimov's juvenile Lucky Starr and the Rings of Saturn (Lucky Starr #6). The hostile power is the Sirians. Quoting the plot summary from Wikipedia:

A Sirian ship then contacts Starr and informs him that the Sirians have built a colony on Titan and claimed it for Sirius, contrary to the traditional principle that inhabitants of one world in a stellar system have sovereignty over the entire system...

Starr conceals himself and his ship in the interior of Mimas; leaves Wessilewsky below the surface with enough supplies to maintain himself for several months...

When asked his reasons, according to a secret plan of his own, Starr replies that Wessilewsky was placed to establish a colony on Mimas. At this, Conway states that by removing Wessilewsky from Mimas, the Sirians violated the very principle they attempted to establish - Devoure has stated earlier that the Sirians have never even approached Mimas earlier, so it is Earth's regardless of whose point of view is taken. Seeing the opportunity, Doremo points out the demonstrated implications of accepting the Sirian view; a war can start literally over every single rock.

This matches your question on every point except that it takes place around Saturn, not Jupiter. (As noted in the comments, book #5 Lucky Star and the Moons of Jupiter was set on Jupiter, so if you were reading the series in order you might have conflated the two.)