I don&#x27;t necessarily think they should be <i>illegal</i>.  I do think that browsers should go out of their way to make life difficult for organizations that want to do this.  If Firefox and Chrome both agreed to hold the line on this issue and say &quot;MITM is always wrong&quot;, forcing prospective MITMers to maintain local hacks, then at least <i>some</i> organizations would listen, even if others continue to do the wrong thing.