Gouldens has won an intellectual property case against Microsoft that IP experts say will swing the balance in favour of defendants.
The High Court ruling has challenged the assumption that judges will slap wide-ranging injunctions on companies that infringe another's patent or copyright.
The ruling comes days after one against French manufacturer Coflexip SA, in which Mr Justice Laddie ruled a plaintiff does not have the right to expect an injunction if the defendant has acted honestly and infringed accidentally.
He said that further offences, which may also be unintentional, should not place the defendant in contempt.
In the Microsoft case, the judge, Alan Steinfeld QC, applied the same principle. Gouldens' client, Plato Technology, admitted selling counterfeit Windows 95 software, but said it had no idea it was bogus. Steinfeld granted an injunction, but only prohibited Plato from dealing in products that it knew, or ought to know, were counterfeit.
Gouldens solicitor Michael McCaghy says it is a significant shift in the law on intellectual property rights.
"In both cases the courts have been willing to restrict those rights to the owner's legal entitlement."
Simmons & Simmons partner Kevin Mooney says the rulings "swing the balance in favour of defendants".
"It's always been normal to give an injunction to enforce the rule that 'thou shalt not infringe again'. But Laddie is saying that it's time to change the practice," he says.
Plato barrister Graham Shirley says: "Apart from having to pay my bill, my clients are very happy."
But he says one implication of the ruling is that "people in the future will hold their hands up and say, 'gosh your honour, I didn't know'."
Carolyn Chia, intellectual property solicitor at Wilde Sapte, says: "This case and the Coflexip case introduces a movement away from the pro-plaintiff stand."
Coflexip is appealing the ruling in its case and Microsoft is also considering an appeal.