JSA, sanctions and universal jobmatch

I have seen a report in the news section that the DWP has made it ‘compulsory’ for JSA claimants to use the universal job match site to look fo job vacancies, and I have looked at the information on the DWP website on the same subject, but nowhere does it say on what authority they have done this: which statutory instrument makes this possible, does anybody know?
I ask because IDS announced a month ago that it was compulsory for claimants to use it and this turned out to be incorrect. i have a suspicion that it might not be all that ‘compulsiory’ but might be incorporated into the general rules about when JC+ staff can issue jobseekers directions.
    This might seem a relatively minor issue to some, but it is not minor if you are a claimant to be threatened with sanctions for not using something when you have no home internet access, which still has security issues, and which in fact is fairly useless for job finding because it has a limited range of both jobs and employers. I have registered to use this universal job match site myself, out of curiousity, and I simply do not believe Grayling’s assertion that 460,000 employers have advertised on it.

Anyway, my question was: what statutory instrument allows the DWP to make use of the universal jobsite compulsory?

Regulation 18(2)(b) of the JSA Regs is probably wide enough to cover it but note 18(3).