They can't, really, it's just that the general populace has not caught on yet.
These judges are suffering from delusions of omnipotence.
Unfortunately their delusions of omnipotence become reality when the other branches of govt meekly accept their decisions. Or perhaps a better analogy for this would be; when they bend over and take it from the Courts on one issue after another.
It would be great if a governor, or President, would simply say, 'enough', and openly defy one of these crazy decisions. They should use their bully pulpit to declare that such decisions are clearly w/o constitutional merit, and as such he cannot in good conscience enforce such a decision. So long as the state legislature, or Congress backed him up, there would be no immediate political fall-out, and if he were articulate and forceful in his engagement with the public, then the people would side with him. This would render such court edicts void, and show everyone that the emperor has no clothes, that they are a paper tiger, w/o any ability to enforce their crazy decisions. Alexander Hamilton said as much even as he was arguing for judicial review.
If such an act led to a sort of Constitutional crisis then that would be a good thing, as it would futher focus the public on the Courts. Then they'd see how on one issue after another, the Courts have acted to impose the values of an elite leftwing on a whole host of issues like abortion, gay marriage, illegal immigration, public nativity scenes, prayer, etc. This could only be good for conservatives, as on each of those the people hold conservative views and they'd take full notice how the Courts are acting to impose by fiat what can't be won in the proper legislative and popular authorities.
Of course this is all wishful thinking. Does anyone think President Bush would defy a SCOTUS imposition of gay marriage/civil unions? Is there a governor out there who would? Even Rush Limbaugh has recently revealed that he doesn't favor such action, which surprised me seeing as how such a mindset is a defacto surrender in the culture war. He said we shouldn't meet lawlessness with lawlessness, and that translates into; 'yes, the Courts do have the right to act like kings, and we should just keep electing Republicans who will give lip service to the battle against judicial activism but once elected do very little about it.'
Its very frustrating.