Yes ... and unfortunately they are complex and ambiguous compared to the UK, which is often cited by French metal detecting fans as an example of how things should be done.
In France they admit that finds are generally not declared due to legal ambiguities.
Article L542-1 of the Code du Patrimoine says you must seek permission from the préfecture if you wish to use a detector to search for items that 'can be of interest to the fields of prehistory, history, art or archaeology'.
In practice, detection fans say no one does this, such permission is rare and is usually given to people working in partnership with professional archaeologists.
In theory this does not apply to detecting as a casual leisure activity not intending to look for 'items of interest to prehistory etc'. The potential difficulty lies in how to prove what your intention was.
The then Culture Minister Jack Lang said if you used one without the specific aims mentioned in the rule, you should just be sure to declare any unexpected historical find to the authorities. This should be by declaration to the mairie.
There is, however, a ban on using a detector in a designated archaeological site – the difficulty here being that these are not always clearly identified. You should also ask permission of the land owner before detecting, in theory including the mairie if it is communal.
The specialist website detecteur-de-metaux.com says it is highly advisable in the case of detecting on someone else’s land to ask the owner to sign a paper agreeing to share anything that you find.
Legally, if you discover treasure trove (un trésor) on someone’s land completely unexpectedly – treasure being something old and valuable hidden on land whose original owner is unknown - it belongs half to you and half to the landowner, if you declare it.
However if you were searching with a detector this may be deemed to have ruled out the unexpected element - the find may therefore be deemed to belong to the owner of the land (in the absence of any agreement to the contrary).
Finally, there are certain areas where a ban has been decreed by the prefect or mayor due to there being a lot of archaeologically sensitive sites or dangers. For example, in Picardy and at Verdun, due to risks of unexploded bombs, as well as on the Normandy beaches. If in doubt, ask the mairie.
It may be advisable to buy your detector from a local specialist and ask their advice, as well as talking to French enthusiasts, perhaps on online forums such as detecteur.net