More than 170 people stripped of weekly ACC payments last year may be affected by a district court decision.
Judge Martin Beattie has ruled that a woman from Hamilton who was unable to work because of a childhood injury is entitled to weekly compensation.
Dominique Vandy fell off a horse at the age of 12, badly injuring her shoulders and hip.
She says she was able to manage part-time work while still at school, but that after she started working full-time, her pain got worse and it quickly became obvious that she wasn't fit for work.
The Accident Compensation Corporation (ACC) argued there was no entitlement to compensation because she wasn't employed at the time of the original accident.
However, in a written decision, Judge Beattie has ruled that there is nothing in the law to say incapacity must immediately follow an injury.
His decision contradicts a ruling made in 2006, known as the Giltrap decision, which was used last year by ACC to cancel payments for 172 long-term claimants.
The Giltrap decision says people are not entitled to weekly compensation if they weren't working at the time when they were injured.
ACC says it will seek leave to appeal against the latest decision. Spokesperson Laurie Edwards says the latest ruling appears inconsistent with the decision in the Giltrap case, and ACC needs the law clarified in order to confidently assess claims.
A lawyer specialising in ACC cases, John Miller, is representing several people who lost their weekly payments as a result, some of whom he says were forced to sell their homes.
Mr Miller says ACC should reinstate their payments until the matter is clarified in the High Court.