write a paraphrased version of the given text.
That kind of obligation is unlikely to be exemptible when the CR5 is equal to or above 50%, unless none of the suppliers imposing such an obligation belongs to the five largest suppliers on the market.
Such a ban will not fulfil the conditions to be exempted if the CR 5 is equal to or greater than 50%, unless any of the contractors to which that prohibition is imposed do not belong to the five strongest contractors in the market.