Then it should be a simple matter for the Republican house to impeach Garland. I'm not sure what remedy congress has for getting rid of an illegal special counsel.
The legal remedy would require the agreement of numerous politicians, most of whom would receive no personal gain and so will be reticent to join in the removal. This is why, when the left needs to remove someone, they result to extralegal (lawfare) or illegal (arkancide) means. Until we are willing to meet them at their level, we will always lose--but on the day we meet them at their level, we will win at the loss of our souls, which is eternally worse.
Congress should do two things:
1. Immediately start impeachment proceedings against Merrick Garland. This is black letter law. Garland, as Attorney General, is blatantly violating the law. No politicizing the charges. This is a slam dunk.
2. Immediately start subpoenaing more witnesses. The instant any government official tries to interfere or object, call them out and remove them from their job for facilitating a violation of the law.
When the other side is violating the law, USE IT AGAINST THEM.