What does the principle of legality in criminal law protect?
The legality principle prevents punishment for conduct not clearly criminalized when committed and requires penalties to rest on law.
Criminal-law doctrine and procedural conditions
Offenses and sanctions must be accessible, foreseeable and sufficiently precise. Administrative rules cannot exceed statutory limits to create a new crime or punishment. Analogy and expansive interpretation cannot establish adverse criminal liability absent from the statute. Criminal analysis separates conduct, the actor, mental element, unlawfulness and culpability. Even when several provisions appear relevant, concurrence, special-rule and apparent-concurrence principles require separate review. The law in force at the time of conduct is compared with later legislation; a harsher rule is not applied retroactively and a more favorable law is assessed as a whole. Facts and supporting evidence matter as much as the name given to an alleged offense.
Evidence, safeguards and case-specific assessment
If criminal law changes after the conduct, old and new regimes are compared as a whole and the more favorable one applies where appropriate. Procedural provisions and security measures require separate classification. The historical text in force at the time should be obtained from official archives as well as the current text. Criminal procedure combines the presumption of innocence with access to counsel, the right to remain silent, reasoned decisions and effective review. Investigative measures are not automatic punishment; legal grounds, proportionality and competent supervision are required. Minutes, video, digital material, witness testimony and expert reports are assessed for lawful acquisition and reliability. Because deadlines can be short, official notice and current procedural rules should be checked without delay in an actual case.