Article III, Section 1: The Judges, both of the supreme and inferior Courts, shall hold their Offices during good Behaviour...
Unfortunately, in the real world, "good behavior" is politically defined, not constitutionally defined. Breyer will never suffer consequences for his views unless We The People made it politically dangerous for Congress to ignore him. Not gonna happen, not in our lifetimes, I'm afraid.
These fools have no idea that they are smoking in the dynamite factory.
I don't know if he could be nailed for treason, but removed? Absolutely. SCOTUS justices can be, and have been, impeached. Look up Samuel Chase in Google sometime.
I believe the biggest error the framers made was to give federal justices lifetime positions. It has given dangerous men like Breyer a chance to destroy this country from within.
There is NO WAY a man with this belief system should be judging anything more important than apple pies at the county fair.