The U.S. Supreme Court, which opened open its 2016-17 term on Monday, will hear arguments on Wednesday in the case of an Illinois man - Bassam Salman - who prosecutors said made nearly $1.2 million trading on inside information about mergers involving clients of Citigroup, where his brother-in-law worked.

It is the first time in 2 decades that the Supreme Court has taken up a case involving insider trading, a crime the U.S. Congress has never defined.

Salman is appealing his 2014 conviction on conspiracy and securities fraud charges, and his 3-year prison sentence.  At issue is whether the government in insider trading cases must prove that an alleged source of corporate secrets - like the brother-in-law - received a tangible benefit like cash in exchange for any tips.  Salman argued that his trading was not illegal as no proof existed that his brother-in-law, in tipping a family member who in turn tipped Salman, received anything beneficial in exchange.

Lawyers and prosecutors say that requiring such proof would make it harder for authorities to pursue insider trading cases, potentially preventing prosecutions in which corporate executives tip friends or relatives without any tangible quid pro quo.