A company doesn't necessarily need to be operating under a Convention Collective, indeed some small businesses do not, but depending on a company's commercial activity, many companies are so required to operate under a Convention Collective. And, if a company is a member of ony one of the Employer Unions, they are also required to  operate under a Convention Collective.

What I mean by softness in consumer demand, insofar as the law makes it easier to fire employees, in addition to the reduction in overtime payments (both timing and amount) that will result from certain measures, companies will find themselves able to pay less; this facilitates precarité and lower salary levels, which are direct reductions in consumer demand all other things being equal. Given the operating multiplier we are at, roughly 1.4 or 1.5 in the delveraging environment we find ourselves in, each Euro taken out of an employees pocket will likely result in 1.40 or 1.50 less in overall consumer demand. The hope is that this will be offset by increased business investment, though there is no empirical evidence that such measures actually spur overall business investment levels.