The judicial branch does not decide who to prosecute. They're supposed to ensure that the law is applied consistently, but prosecutorial discretion is entirely up to the DoJ and at least nominally is part of the executive branch (for federal crimes). They also don't directly decide whether someone is convicted in most cases; a judge can throw out a meritless case or in rare cases vacate a jury verdict, but the jury verdict itself is outside of any of the three branches by design.

In any case though, this is isn't super relevant to my comment you replied to. The parent comment claimed that the debate about the law was purely theater, and I argued that it might not be because someone could get prosecuted for it if the law isn't on the books. Whether the DoJ should try to prosecute someone for something is not the same as whether they will try to. The DoJ has tended to operate in a somewhat removed way from the whims of the president in the aftermath of Watergate, but that's a precedent that's been pretty clearly been eroded in recent years. That doesn't mean political prosecutions will be successful, but using legalism as a way of trying to enforce one's political agenda is not a new phenomenon; the Bush administration had lawyers write up opinions justifying their use of "enhanced interrogation" because being able to couch one's actions in legal terms is one of many ways to try to build support (or mitigate opposition) to them. Having laws that say something is not allowed has at least some effect even when people try to get away with violating them, even if it's only in the form of soft pressure.