As a result of legislation championed by NYSUT, the state AFL-CIO and other unions across the state, (signed into law 4/2017), union members in New York can deduct their union dues from the state income taxes if they itemize.
While not a dollar-for-dollar deduction for your overall union dues, this deduction will offset your taxable income if you itemize your New York state income taxes.
Consult with your personal tax preparer to confirm your own situation.
More information can be found here.
https://nysaflcio.org/news/deductmydues