If the court annuls all or part of a collective agreement or convention, it may decide, if it appears to it that the retroactive effect of this annulment is likely to have manifestly excessive consequences by reason both of the effects that this act has produced and the situations that may have arisen when it was in force and of the general interest that may be attached to the temporary maintenance of its effects, that the annulment will produce its effects only for the future or to modulate the effects of its decision over time, subject to legal proceedings already commenced on the date of its decision on the same basis.