Warning signs -- how to warn people about the risk of prosecution

This picture was recently sent to me, with some comments about the oddness of the English structure of the message. It certainly reads rather strangely, but what exactly is the problem?

'Waiting' is a noun form that describes an action performed by a motorist, and as such is like words such as 'parking' and 'stopping'. These are uncountable nouns, and you will often see these words in signs preceded by the word 'no', as in the example below. ​

We may ask, if we can say 'No Parking', can't we also say 'Parking will be prosecuted'? And by the same token, if we can say 'No Waiting', can't we say 'Waiting will be prosecuted'?

Well, take a look at standard English sign that communicates both these points:

Note the format here: first the general rule is stated ('No parking'), and second the consequence of breaking the rule is given. When breaking the rule will result in prosecution or a fine, we have to mention a *person* because it is generally people who are prosecuted or fined, not actions. In most signs like this, you will find words like 'offenders', 'violators', 'trespassers' etc. used to refer to those people who break the rules and are subject to prosecution. Here is another example:

In summary, if we want to warn about the risk of prosecution, in English we normally refer to the people who run the risk of prosecution. 

NOT Spitting will be prosecuted.
BUT  No spitting. Offenders will be prosecuted.

NOT Dumping of rubbish will be prosecuted.
BUT  No dumping of rubbish. People caught dumping will be prosecuted.

NOT Trespassing will be prosecuted.
BUT  No trespassing. Trespassers will be prosecuted.

So -- how to redraft our original sign? Here's a version in a much more standard English:

NO VEHICLE WAITING. Offenders will be prosecuted without warning.