Campaigners are seeking to overturn a decision by NHS bosses to recommend GPs no longer prescribe homeopathy.
The British Homeopathic Association has won the right to have a judicial review of the move.
It was proposed last year by NHS England after a consultation, which the BHA is arguing was flawed.
Simon Stevens, the chief executive of NHS England, has described homeopathy as "at best a placebo and a misuse of scarce NHS funds".
At the High Court, Richard Clayton QC, who is representing the BHA, said the consultation, which ran ahead of the decision in November, had been overly complicated and failed to present both sides of the argument.
He said there was "ample" evidence that homeopathy worked but the consultation had been "completely one-sided".
He also said the consultation documents were too technical and not understandable to the "ordinary person".
NHS England rejects the accusations.
What is homeopathy?
Homeopathy is based on the concept that diluting a version of a substance that causes illness has healing properties.
So pollen or grass could be used to create a homeopathic hay-fever remedy.
One part of the substance is mixed with 99 parts of water or alcohol, and this is repeated six times in a "6c" formulation or 30 times in a "30c" formulation.
The end result is combined with a lactose (sugar) tablet.
Homeopaths say the more diluted it is, the greater the effect.
Common homeopathic treatments are for asthma, ear infections, hay fever, depression, stress, anxiety, allergy and arthritis.
The NHS itself says: "There is no good-quality evidence that homeopathy is effective as a treatment for any health condition."
The guidance issued by NHS England focused on a range of different treatments bosses wanted GPs to stop prescribing – of which homeopathy was just one.
Spending on homeopathy prescriptions accounted for about £92,000 last year.