The government has given the left-leaning Korean Teachers and Educational Workers’ Union an ultimatum that it would be outlawed unless it amends its constitution that accepts dismissed teachers as members.

The Ministry of Employment and Labor served the final notice Monday, telling the 60,000-member powerful union to follow its order by Oct. 23 or face losing its hard-won legal status.

Under the current law on trade unions, an organization is not regarded as a trade union if it allows those who are not workers to join it. The law also authorizes the government to order a union to correct this illegal practice.

If a union fails to follow the instruction, the government can outlaw it. An outlawed union loses the right to conclude a collective agreement with its employer and is deprived of other legal benefits.

The government’s move, quite expectedly, touched off vehement resistance from the union. Defining the ultimatum as “a declaration of war against labor,” the union’s leadership pledged “an all-out struggle,” including going on the indefinite hunger strike from today.

The union plans to form an alliance with civic groups and opposition lawmakers to resist the government’s “suppression of labor.” It also plans to instruct all its members to take Oct. 18 and 19 off and come to Seoul for a large-scale protest rally.

The union’s campaign will also include requesting the International Labor Organization to intervene to stop the move and filing a complaint with the Constitutional Court against the trade union law.

Currently, the union’s membership includes some 20 fired educators, of whom the government says nine are not qualified.

In fact, this is not the first time that the government told the union to revise its constitution. It issued its first order in March 2010. The union defied it, saying that it had the intrinsic right to decide the qualification of its members.

Three months later, the union filed a suit with the Seoul Administrative Court to nullify the government instruction. But the court ruled against it. The Seoul High Court and the Supreme Court handed down the same verdict in 2011 and 2012, respectively.

Last September, the ministry issued its second order to the union, only to be ignored again. In May and June this year, ministry officials met union leaders to urge them to change their mind.

It is against this backdrop that the government served its ultimatum. It says it has given the union enough chances to amend its constitution.

Yet the union argues that it is the current law on trade unions that needs to be rewritten. It points out that teachers’ unions in many advanced countries accept unemployed teachers and retired educators as members.

In fact, the ILO recommended last year that the Korean government abolish the controversial clause in the trade union law that denies unemployed or terminated workers the right to join a union.

But the union should respect the current law as long as it remains in effect. The law has been upheld by the Supreme Court. If the union wants to reform the current system, it should promote it in a legitimate way. It will first have to secure public support for its position and then pressure the government to rewrite the law.