While they were banned since this past March 31st by a decree ordered by Police Prefect Didier Lallement the Bois de Boulogne and Bois de Vincennes woods are fully reopening as deconfinement starts.
So, starting from May 11th, you can now walk around the woods, as well as around the Lac Inférieur at the Bois de Boulogne and along the Lac Daumesnil, the Lac des Minimes and the Lac de Saint-Mandé.
This decision was released in a press release from the Paris City Hall. On the occasion, the city hall said: the Police Prefect and the Paris city hall "want to hail efforts made by all Parisians since the confinement has started. These efforts enable to contain the spread of the epidemic and make sure patients could be taken care of at the hospitals".
Please note that the Seine Riverbanks, the Esplanade des Invalides and the Champ-de-Mars in Paris are opening again. Yet, since Paris is in a red area, parks and gardens cannot reopen now, but the "Police prefect will look at the situation in partnership with Paris city hall, as soon as constraints and health data evolve".
For the record, if you are allowed to go to the Bois de Boulogne and the Bois de Vincennes to enjoy a breath of fresh air and work out, any gathering over 10 people remain banned.