Should recording a cop in a public place be illegal?

You'd think that recording what a police officer says in a public setting would be fair game, but in some places it isn't:

Drew is a free-speech advocate; his State Street appearance was part of an ongoing protest against a Chicago law restricting where artists can sell their wares. A Chicago police officer noticed Drew in the off-limits area, and told him to move along.

Drew was hoping to get arrested to test the city's law; he got his wish. Prosecutors charged him with two misdemeanors. He was not expecting what came next. After police found a small recording device in his belongings, Drew was charged with a felony for violating the Illinois eavesdropping law, which requires all involved to consent to any audio recording

Full article at NPR