He wasn't "allegedly" arrested for downloading files illegally. He was never accused of or charged with copyright infringement. He was accused of various forms of "hacking" and trespassing.
> had been arrested for illegally downloading millions of articles from JSTOR
The OP, as you pointed out, says illegally downloading. The illegal part, ostensibly, comes from the alleged "hacking". There is nothing about copyright infringement implied here, though yes, that's the natural connotation of "illegal download"
