Most Imperial law enforcement will be MoJ, and have cooperative agreements, bilateral or multilateral, with member worlds. So while the local world may have the Imperials stop at the 10D, and/or the XT line, usually they won't. MoJ folks will have locals do most of their strong-arm stuff, usually through a joint Imperial-local task force, which is about 5%/95% on the manpower, and 80%/20% on the money and tech. Such Task Forces will normally have mutual cooperation agreements between worlds in neighboring systems, and may thus be multi-jurisdictional. That is not to say that these are required or even strongly encouraged by the MoJ, but rather they are found to be mutually beneficial in most cases by most parties. The MoJ's stock in trade is garnering cooperation while respecting the sovereignty of the member worlds. The IISS is almost always sought for their wide contacts and expertise, and are free with intel support for such law enforcement endeavors, but usually they keep their relatively minor muscle for their own in-house pet projects.
Scouts hunt pirates, and the IN kills them. Scouts have law enforcement powers, but more important things to do, usually, than to focus on law enforcement. Combat Search and Rescue is usually part of the combat force, which is to say IN. CSAR in the IISS is an outgrowth of the fact that sometimes agents get snatched. Of these cases, usually there is either an exchange, or a covert rescue attempt, if the agent is valuable enough. Sometimes, rarely, an asset or agent that is valuable enough may be held in a secure enough facility or missing in a hot enough area that the S-3 may used in a CSAR or HR role. This is the exceptional case, though. If the local IISS has a pet project, he may actually send S-3 folks on it; or he may decide that they are too valuable, and the pet project too obscure to use such high profile assets, and cobble something together out of DD's. Stranger things have happened in the black....
