Simon Young told CBS News he sued the Hong Kong government after asylum-seekers faced persecution in their home countries.
The court ruled that the government must change its asylum system and ordered that the laws be standardized.
Young said any asylum request would be unresolved until the legal changes are made, which could take years.
The wait could allow Snowden to stall.
"We have a system that is slowly processing individuals, and in some respect has stalled, " Young said.
Snowden, 29, previously told news sources that he was in Hong Kong to seek asylum.
But Hong Kong officials implied they would cooperate with the United States.
"I think it would be wisest for him to leave Hong Kong," said former secretary of security Regina Ip.