Yes you can still use and extendable lead, but you must not extend it beyond two metres if directed to place your dog on a lead of no more than 2m in length.
Gallwch ddefnyddio tennyn estynadwy, ond ni ddylech ei estyn y tu hwnt i ddau fetr os gofynnir i chi roi eich ci ar dennyn nad yw'n fwy na dau fetr o hyd.