While the determination of legality typically depends on the specific circumstances, context, and jurisdiction, there are numerous actions that can be deemed illegal under various laws. In Australia, for example, offences can range from minor infractions to serious crimes, often defined by local, state, or federal legislation. To ascertain whether a particular action is illegal, one must consider the relevant laws and regulations that apply, alongside any potential defences or exceptions. If you have a specific scenario in mind, it would be best to consult legal resources or seek advice from a qualified legal professional to obtain clarity on the issue.