No it can't. This is nothing to do with DEFRA. TB is not considered as infectious as the mentioned diseases, DEFRA have no jurisdiction.
Since they are issuing the licenses I'd have thought it has EVERYTHING to do with DEFRA.
As said previously, it looks like only 70% of the landholding has to agree. I think we can take that to mean 70% of the land area rather than of landowners. If someone knows better please speak up.
Also, as said previously, whilst "enforcement" may be problematic on land belong to those whose agreement has been withheld, though I'm sure national interest laws could be invoked to overturn the misguided adherence to rights of those who choose to opt out, it would probably be neither desirable nor necessary to do that as one only has to wait till the badgers have crossed boundaries onto land where agreement has not been withheld.
It would probably serve many people well to remember that we are talking about human food production here (and not just production economics either, even though that side of the equation is becoming ever more critical in itself) and whilst I'm sure no-one wishes Badgers erradicated completely it does seem to have been clearly indicated that human food supply and health are being threatened by a disease also transmitted to humans via both Badgers and cattle, or else this course of action would never have been contemplated let alone sanctioned in the first place.
To tell the truth I totally agree with Stag1933 about the desirability of seeing Badger predation pressure on other, ground living, wildlife reduced too. And very much look forward to seeing how matters develop, in that respect.
The proposed trials will hopefully answer all the theorists questions, whether they like the answers or not... and I suspect the antis know that many of their ideas are highly questionable and for that reason are probably somewhat, unusually, anxious about the potential outcomes.