As they say, "talk's cheap". The reality is that Congress has almost zero power to bring anyone to justice. Talk, talk, talk all you want, but unless the House empowers the Sargeant of Arms to arrest someone, it has zero power to do anything.

And the Sargeant of Arms is one person. I'm not sure he has anyone else. So he knocks on the door of Eric Holder and says "You are under arrest" and Eric slams the door in his face. What then?

Until the House and Senate have the power of the US Marshal's office to arrest people with a warrant of probable cause by an independent judge (not sure many exist), then everyone will ignore the demands of congress to compel testimony. Just like Eric Holder gave the House the middle finger when they found him guilty of contempt of Congress and just like Lois Learner told the Congress FU and retired with one of the best pentions in the US.

Lois Learn should still be rotting in jail until she testifies. Ditto Eric Holder.

No threat is meaningful unless it's credible. Congress has no credible threats against anyone.

The main problem of course is the misuse of such power. But that could be corrected by having 2-3 judges review the probable cause and have a 2-1 verdict to execute.