Jean Tirole: Leaving the euro would have serious consequences for France

France would inspire less trust than it does now. Restoring the franc could cause a sovereign default. The debts of the state, banks and French companies, all in euros, would become more difficult to repay if revenue were recorded in francs, a weak currency. Households would also lose out due to the depreciation in national currency and the concomitant rise in the cost of imports. Yet protectionism is not a magic wand for citizens in France, or elsewhere for that matter.
 
https://www.ft.com/content/8d5887d2-1f8a-11e7-b7d3-163f5a7f229c