Would a tautological law have any effect?

Question

Is there any case where a law saying something like "Any person who commits theft is guilty of theft" would have any effect?

Answer 1

"Any person who commits theft is guilty of theft"

This is not tautological. "Any person who commits theft commits theft" or perhaps "Any person who commits theft is a thief" is tautological. But the hypothetical law as written makes theft something that someone can be guilty of, that is, theft is an offence and illegal. The exact consequences depend on other provisions and the legal system itself.

If a common law jurisdiction abandons common law offences in favour of a criminal code and such code does not contain "any person who commits theft is guilty of theft", then theft would be legal (or at least not criminalized by such code).

Theft has to have an operable definition for the law to be effective, but the definition does not have to be explicit in the statutes when there are other sources of laws. The courts are meant to interpret the words in law reasonably, relying on ordinary definitions of expressions, the discernible intention of the legislature, history and social development.

There can be unconstitutionally (or otherwise unacceptably) vague laws, but in common law jurisdictions, at least the usual crimes like theft and murder have been interpreted by the courts over hundreds of years with a rich body of case law and legal literature. Crimes like piracy benefit from a multitude of internationals conventions and case laws in many jurisdictions, for example, the Canadian definition of piracy is almost a tautology:

74 (1) Every one commits piracy who does any act that, by the law of nations, is piracy.

Of course, the operative provision is exactly the one with the words "is guilty of"

(2) Every one who commits piracy while in or out of Canada is guilty of an indictable offence and liable to imprisonment for life.

Answer 2

Some German laws are written almost that way

Section 211 (German) Murder under specific aggravating circumstances (Mord)

(1) Whoever commits murder under the conditions of this provision incurs a penalty of imprisonment for life.

(2) A murderer under this provision is someone who kills a person out of a lust to kill, to obtain sexual gratification, out of greed or otherwise base motives, perfidiously or cruelly or by means constituting a public danger or to facilitate or cover up another offence.

The definition here is defining someone commits murder if he is a murderer... for which they do provide a definition, which is very akin to Murder 1st degree in many states of the US.

Section 212 (German) Murder (Totschlag)

(1) Whoever kills a person without being a murderer under the conditions of section 211 incurs a penalty of imprisonment for a term of at least five years.

And in 212 they define that someone commits still murder if they kill someone but are not a murderer - in Germany that's technically called Totschlag, in US law that's often considered something like murder in the 2nd or 3rd degree. Which is again different from less serious case of murder (minderschwerer Totschlag, StGB §213), killing by neglect (Fahrlässige Tötung, StGB §222), bodily harm resulting in death (Körperverletzung mit Todesfolge, StGB §227)...

Answer 3

In order for a law like this to have any effect, it would need to be accompanied by a clear definition of what constitutes theft. For example, the law could stipulate that theft is taking something without the owner's consent, with the intent to permanently deprive the owner of its use. This would provide a clear and objective standard against which to measure alleged instances of theft. Without such a definition, the law would be little more than a empty statement. Furthermore, even if the law was accompanied by a clear definition of theft, it is doubtful that it would have much of an impact. After all, those who are inclined to commit theft are unlikely to be deterred by the existence of a law against it. In short, while a law against theft might theoretically have some effect, it is unlikely to be significant.