When Jeremy Hunt rules on News Corporation's proposed takeover of BSkyB, the Secretary of State will not have a completely free hand.
Any decision he makes must be sufficiently robust to withstand a legal challenge from interested parties who have huge vested interests in either of the two outcomes. To help Mr Hunt bind his decision in sound reasoning, he can rely on a small army of Whitehall lawyers and outside experts in competition law. For the bid to go through, it must be established that Mr Murdoch will not end up holding a dominant position in the media marketplace.
The European Commission has already cleared the way for the deal and the media regulator Ofcom's view of its impact on the industry is expected soon. So there will be no shortage of written legal opinion from which Mr Hunt's advisers can draw. If all the opinion is one way, he will find it difficult to recommend the opposite course of action.
Central to his advisers' concerns will be the fact that Mr Hunt is a Secretary of State whose decisions are subject to a judicial review challenge in the High Court. The key test the judges consider is reasonableness: he will have to show that any decision taken was one that an independent reasonable person could have come to.
But Mr Hunt's first key decision will be whether to call for a full Competition Commission inquiry. The proposed deal has become so controversial the Government may find it difficult to resist asking the Commission for help.
If Mr Hunt gives the go-ahead to the Commission, he will then have to decide whether to support its findings. What is certain is that the whole process will drag on for many months, which might suit the Coalition Government very well.