Lots of people in this thread are acting as if the court held that the arms sale was moral, or even a good idea. Courts don't work like that (at least, Judicial Review cases in England don't).

The court was asked to block arms sales on the grounds that the gov'ts decision to sell arms to Saudi Arabia was Wednesbury unreasonable. For a decision to be Wednesbury unreasonable, it must be so irrational that no sensible person could have arrived at it.[0]

This is a really high bar.

The court held that the decision to sell arms didn't meet this bar. This was the expected outcome — it's pretty rare for government decisions to be overturned for Wednesbury irrationality. This case was a long shot by the CAAT. This doesn't mean the court thought arms sale was good, moral, or anything else. But English courts doesn't have the power to strike down decisions (that are within the power of the government to make under statute or common law) for not being good or moral.

(IANAL).

[0] https://en.wikipedia.org/wiki/Associated_Provincial_Picture_...