"If you are living in a designated control area, you need a licence in order to have a horse. A licence normally lasts for a year. The local authority keeps a publicly available register of all licences issued."
"If you wish to ride your horse on a public road, you may do so provided that the horse has a licence, is fitted with a bridle and is under the control of someone over 16 years of age."
Generally, this is the entire area of your local authority/council.
A horse licence costs around €30, but this varies between councils. Dublin City Council charge €31.74.
Following submission of a licence application the Council’s veterinary officer will contact the horse owner to arrange an inspection.
Your local authority/council.
The Gardaí or staff authorised by the local authority may decide to inspect your horse and you must allow them to do this. They can also ask you to produce evidence of a horse licence. They have fairly extensive powers of search and arrest if they suspect cruelty to horses.
The legislation specifies several offences, including failure to remove a horse from a public place or control area and dangerous use of a horse. You may be arrested without warrant for most of these offences. If convicted, you may be fined or imprisoned (or both) and you may be disqualified from keeping a horse for a period. The court may seize the horse and dispose of it as it sees fit.
Sources Include: Citizen Information