I work for a public employer which has a lobor union I had no choice in joining, during contract negotiations had fell through and the labor force

As a general matter, under the National Labor Relations Act, a union member can be fined by the union for working during a valid strike. This result is the same whether the employee in question was an avid union supporter or a grudging member. The fines can be avoided by resigning from the union prior to crossing the picket line.