I reckon cases that span jurisdictions are interesting. The law is confronted with them more and more often as technology and transport cuts across borders with greater ease.
Common law courts struggled with such cases. The basic premise under the common law was “all crime is local” and jurisdiction over a crime lay with the country where the crime was committed: Macleod v Attorney-General (NSW)  AC 455 at 458.
But what happened when the acts comprising a crime occurred in one country, but the criminal intention took place in another? At various times courts used a terminatory or initiatory theory of jurisdiction, deciding that crimes occurred where an offence finished or started.
In Board of Trade v Owen  AC 602 the House of Lords concluded that a conspiracy formed in England to commit a crime in Germany was not a crime in England.
But in Treacy v DPP  AC 537 the Lords decided that a man who sent a blackmail demand by letter posted in England to Germany committed the offence in the UK.
In Thompson v The Queen  169 CLR 1, the High Court considered a murder that happened near the ACT-NSW border. It said if the question of locality was in dispute, it must be proved on the balance of probabilities.
Earlier in Ward v The Queen (1980) 142 CLR 308, the High Court considered if a murder on the Murray occurred in Victoria or New South Wales. The deadly shot was fired in Victoria (from the top of the riverbank); the victim was at the water’s edge on the Victorian side of the river.
The border of NSW was the River Murray (its south side) — and the Court held that it ended at the top of the water-retaining land-contour. Or, simply, the top of the river bank. So, Ward’s victim died in NSW. The High Court considered the terminatory theory of crime determined jurisdiction. And that meant his murder conviction in the Victorian Supreme Court was set aside! (The NSW Lands Department has very useful publications on this, and there’s some general information on borders in the GeoScience Australia website too.)
The High Court later moved to a more pragmatic view in Lipohar v The Queen (1999) 200 CLR 485. That case dealt with a cross-border conspiracy focusing on a property in Melbourne, with the conspirators in South Australia, Queensland and Malaysia!
The result was that the High Court decided there is a single unified Common Law of Australia, and the common-law offence of conspiracy could occur in and be tried in any jurisdiction so long as there was a real connection between the State and offence. That meant the trial in South Australia was valid. (Similarly, the offence could have been tried in Victorian or Queensland, but that was a choice for the investigating and prosecuting authorities. A trial in any one state would entitled the accused to a plea of autrefois acquit or autrefois convict if later charged in another state.)
Lipohar considered a common law offence, but I think courts are likely to take a similar approach for statutory offences too. (We know that stalking can cross borders: see DPP v Sutcliffe  VSC 43.)
Applying this sort of reasoning, offences such as breaching intervention orders or using carriage services to menace or harass probably also occur in multiple places. (Consider a breach of an intervention order alleged by proscribed telephone calls when the caller is in Dandenong and the recipient in Frankston. Where does the offence occur?)
(Jurisdiction for offences on aircraft flying to or from or within Australia are dealt with by the Crimes (Aviation) Act 1991 (Cth). Offences at sea are covered by the Crimes at Sea Act 1999 – logically enough.)
A practical issue for investigators in all of these examples is to understand which law to apply. It’s not an issue that courts have dealt with very often, and so there’s been little curial guidance for investigators.
Last week the Supreme Court held in Wallce v Debs  VSC 355 that an investigation in Victoria by non-Victorian police for offences that occurred outside Victoria (and would presumably be prosecuted outside Victoria) did not fall within the scope of Victorian investigation law.
That particular case concerned Crimes Act 1958 s 464B (questioning a person for a different offence to the one they’re held in custody for). But I imagine the same reasoning would apply for the other provisions of Part 3, Div 1, sub-div 30A.
Put simply, if Victorian police go to, say, Queensland to interview a person and want to present that evidence in a Victorian court, they need to comply with Victorian investigation law.
If Queensland police come to Victoria to interview a person and want to present that evidence in a Queensland court, they need to comply with Queensland investigation law.
But they will also need to observe local substantive legislative requirements about gaining access to suspects (such as arrest and time in custody, or access when already in custody) and so require the assistance of local colleagues.
An extreme example might be R v Thomas (2006) 14 VR 475, where Jack Thomas was interrogated in Pakistan by Australian Federal Police members purportedly in accordance with Australian domestic law. That appeal was on different issues — mainly voluntariness of admissions — but seemed to accept an interview to be used in an Australian court would be conducted in accordance with Australian laws, though it took place in Pakistan.
The Standing Committee of Attorneys-General is continuing its focus on cross-border investigations (started back in 2003 and appearing in Victorian law in the Crimes (Assumed Identities) Act 2004 and Crimes (Controlled Operations) Act 2004). So we might yet see more legislation on this topic in the future.