“There can be no crime, there can be no misdemeanor without a law written or unwritten, express or implied.”

A back handed common law reference that gets somewhat lost in the weeds of the word salad — definitely more accurate than not. At natural law — the narrowly defined "the laws of nature and of nature's God" (Declaration of Independence), a law need not be written to exist. Gravity for example; gravity to date has not ben completely or exactly defined while, we all know of its existence by person experience. At man's administration of natural law, due process demands / requires a standard which includes a lawful definition of a/the crime.

'There can be no crime without a law' but can a law be written or unwritten, express or implied?  The interpretation of the supposed law is still required — that is to say, written, not merely implied.

I thought there could be no crime without mens rea, a malicious intent.  First there has to be an injury to life, liberty, property.  A jury may judge whether the injury was intentional, if so, it is criminal according to the Common Law.  If unintentional, then no crime, but still amends are due if the injured party does not  forgive the violation.