Susan Coen, a lawyer for the Canadian Union of Public Employees, said the law breaks charter rights that guarantee the right to association.
"The bill is devastating upon the charter values and principles," Coen told arbitrator James Dorsey during the hearing in Halifax.
The lawyer for the Nova Scotia Government and General Employees Union also argued that the law is unnecessary and an effort by the government to interfere with unions.
"The government intends to take workers away from the unions they have chosen," said Drew Plaxton during his submission. "We suggest with respect that it is contrary to the charter."
The Health Authorities Act merges the number of health districts from 10 to two by April 1. It also created an arbitration process to reduce the number of bargaining units for about 24,000 health workers from 50 to four.
CUPE, which represents about 4,700 health workers, has argued that the province could achieve its goal of streamlining health care's bargaining structure by creating a bargaining association that would allow union members to remain in their existing units while forming a coalition during labour talks.
But Patrick Saulnier, a lawyer for the health authorities, said CUPE's proposed bargaining association may not even be a legal union under existing labour legislation.
The Nova Scotia Nurses Union stands to gain members under the change in bargaining structure.
The lawyer for that union, which represents 5,166 employees who are covered by the law, said it is best suited to represent registered nurses and licensed practical nurses if Dorsey decides to follow the government's process.
Dorsey has previously ruled in a preliminary decision that he may balance constitutional arguments against some provisions of the legislation. He is expected to deliver a decision by Jan. 1.