It depends on which standard it fails to meet. If a product fails to meet a safety standard or mandated legislative standard it should not be on sale and it will often be ordered that it is recalled and the public informed as such.
If a product fails to meet some standard a seller or manufacturer explicitly claims or implies it meets; the seller or manufacturer can be ordered to stop claiming or implying as such, and purchasers will usually be entitled to refunds, repairs or replacement if they seek them.
That's the case in the EU and UK. The situation may differ in other jurisdictions.