Article L2511-1 of the French Labour Code
The exercise of the right to strike may not justify termination of the employment contract, except in the event of gross negligence attributable to the employee. Exercising the right to strike may not give rise to any discriminatory measure as referred to in article L. 1132-2, in particular with regard to pay and social benefits. Any dismissal made in the absence of gross misconduct is automatically null and void.