delegitimise

/D EH1 L IH0 JH IH1 T AH0 M AY0 Z/
verb
  1. 1

    To make something less legitimate.

  2. 2

    To make something illegal that was previously legal.

Source: https://en.wiktionary.org/wiki/delegitimise, https://en.wiktionary.org/wiki/delegitimize