ICE is making a lot of inappropriate arrests in state courts. here and elsewhere. But only because our elected and appointed officials let them. They have no right to be in a state courthouse. The state controls who can be there. It has the absolute right to do so, under the 10th amendment, so long as that doesn’t interfere with the basic rights of the people, such as freedom of speech of a public trial (and the right to a public trial is something the defendant always has a right to waive when it suits his/her interests). Regardless of the public’s general right to be there, the courts can always restrict otherwise lawful activities permitted in their courthouses. For example, most ban cameras and cell phones without prior permission.
So why not ban ICE? They have no legal right to be there. They are there only at sufferance of the state government. If they want to stand on a public sidewalk and arrest people, that’s their right. But the courthouse and its grounds can and should be restricted to legitimate court business only. Contact your legislators and ask them to prohibit ICE raids on our courthouses.