Johnson was given a 12-month suspension in August after her horse, Luke Skywalker 46, tested positive for banned local anaesthetic pramoxine during a competition in Wellington in the United States on January 21.

An FEI Tribunal studied the case and issued the ban, which was backdated to begin on April 4, 2017, the date when she was provisionally suspended for three months.

As the substance pramoxine will be reclassified from a banned substance to controlled medication, effective from January 1, 2018, the two parties - Johnson and the FEI - ultimately agreed a settlement, which was approved by CAS.

Under the terms of the settlement, Johnson's period of ineligibility has been reduced from one year to three months, from April 5, 2017 - the date of notification - until July 5, 2017 and she is therefore now cleared to compete.

The CAS arbitration costs will be borne equally by the parties.

"Given the fact that pramoxine has been recently reclassified as a controlled medication, effective as of January 1, 2018, the FEI agreed as a matter of fairness and based on the principle of proportionality, that the period of ineligibility initially imposed by the FEI Tribunal should be reduced," FEI legal director Mikael Rentsch said.

"Three months was deemed appropriate given the circumstances."

Johnson was also fined CHF2,000 (£1,600/$2,100/€1,700) in August and had to pay CHF3,000 (£2,300/$3,100/€2,600) in legal costs.

A hearing heard that the horse's groom, Sergio Molinero, had bought ointment to treat Luke Skywalker's cuts.

This had been used before and was allowed under doping rules, but he bought the incorrect product at a Walmart store which caused the horse to test positive.

"I found the triple antibiotic on the shelves in the same spot it always is and pulled four tubes of it off the shelves," Molinero said, according to documents published by the FEI.

"I believed at the time I was buying the same triple antibiotic we always buy which is okay under the anti-doping rules.

"I now realise after Paige was able to find my receipt for the purchase that I made a mistake and pulled the wrong tube off the shelf because it looked so much like the one we always use.

"I now see that I mistakenly bought triple antibiotic with pain relief, and the pain relief contains pramoxine."

The FEI ruled that Johnson did not take "every conceivable effort" to avoid a banned substance entering the horse's system.

They ruled that she was negligent but that her fault was not significant, stating that Johnson "seems to generally take good care for the welfare of her horses, and generally has good anti-doping procedures in place".