In the movie "Wall Street" (1987) Gordon Gecko has his lackey Bud Fox follow a rival around to try and figure out what he's going to invest in, so they can unde

In the movie "Wall Street" (1987) Gordon Gecko has his lackey Bud Fox follow a rival around to try and figure out what he's going to invest in, so they can undercut him. He follows him to a private jet and finds out it's flying to mid-sized city that happens to be the corporate headquarters of a particular company. In the movie it's sort of implied that this activity is illegal. I wonder if it actually was, and if so, why that would be different than what those hedge fund guys you reference were doing?