The Food and Drug Administration has no hard and fast rules regarding purchasing contacts without a prescription but specifically advises against doing so. The FDA classifies contact lenses, even decorative lenses, as medical devices that require a prescription.
The FDA encourages individuals to purchase contact lenses from a vendor who sells FDA-approved or cleared contact lenses and who verifies a doctor's prescription before filling it. The vendor should ask for the doctor's name and phone number if this information does not appear on the prescription.
It is not safe to purchase contact lenses, even if only decorative, from a street vendor, a Halloween store, a novelty store, a flea market or a beauty supply store.