For union-strong Hawaii, the negligible membership erosion due to a recent landmark U.S. Supreme Court ruling has to be encouraging, for now.

Before the June 27 decision on Janus v. American Federation of State, County and Municipal Employees, Hawaii unions had feared that an “unfavorable” ruling might lead to an exodus of dues-paying members. The anti-union decision did come, 5-4, which now prevents public unions from collecting mandatory fees from union-covered members who want to opt out of paying them. The unions had worried that workers, increasingly, would become “free riders” — enjoying the benefits and protection of a public union, without paying their so-called fair share.

Now, Hawaii’s public unions say their numbers remain strong, with very few members opting out of paying dues; nor has there been significant funding lost from the loss of service fees that previously had been charged to nonmembers, said labor attorney Tony Gill in a Monday forum hosted by the Grassroot Institute of Hawaii.

Still, it’s been only three months since Janus — so the unions will need to work mightily to keep convincing their people about the range of benefits of paid membership, not least of which is maintaining strength in numbers.

The solid membership retention so far also is thanks to a new state law, passed and signed just two months before the Janus decision, that limits a member’s opt-out period each year to the 30-day window prior to his or her first union-deduction anniversary date. The constitutionality of that law, Act 7, is expected to draw legal challenge. But its very passage shows just how powerful public labor remains in union-strong Hawaii.