I noticed that the recent British headline 'Stop this Royal Circus' has been translated in the French media as 'Stop au cirque royal'. I take it that this French 'Stop' is imperative. But is it normally followed by the preposition 'à'?
This construction is deceptive to the reader of English. The verb that is extracted from the English "to stop" is not "stop" in French, but "stopper".
An imperative would not be used in French.
Stoppe ce cirque royal
Instead an infinitive with the force of an imperative is what would be used.
- Stopper ce cirque royal.
In "Stop à ce cirque royal", "stop" is a noun.
(TLFi) stop Interj. et subst. masc.
It is an ellipsis as in "Non à ce cirque royal".
Nous disons non à ce cirque royal. — Il faut dire non à ce cirque royal. — etc. — Untel a dit non à ce cirque royal. — etc.
Il faut mettre un stop à ce cirque royal. — Nous disons stop à ce cirque royal. — etc.