Horse owners in Somerset are being warned to get passports for their animals as a matter of urgency.
New regulations mean that after 28 February 2005, no-one will be allowed to sell a horse or move it from one place to another without a passport.
Somerset County Council launched a leafleting campaign at shows, stables and vet practices over the summer.
But a spokesman said a "significant number" of owners had still not applied in time for the 1 July 2004 deadline.
A horse without a passport will not be able to take part in a gymkhana, hunter trial, a race or any sort of competitive event.
Councillor Hazel Prior-Sankey, who is responsible for community protection in Somerset, said: "It's vital that they act now.
"Any that don't will find their horse is un-saleable and will be unable to leave the environs of its field or stable."
Passport applications can be obtained from a list of authorised passport issuing organisations (PIOs) available from Defra.
Owners failing to comply with the regulations face a £5,000 fine, three-months imprisonment, or both.