Free (Handout).

Two of the United States' largest telecom companies, Bellevue, Washington-based T-Mobile USA Inc. and Overland Park, Kansas-based Sprint Corp., recently announced their decision to merge, a move that would reduce the number of major telecom competitors in the country from four to three.

The announcement made on Sunday raised eyebrows due to potential antitrust concerns. According to lawyers and other antitrust experts following the case, the legal departments at both companies will have plenty of issues to think through, including the deal's potential effect on the U.S. telecom market as well as its possible international implications.

Andre Barlow, a partner at Doyle, Barlow & Mazard focused on antitrust law, said it's likely lawyers on both sides have been busy for a while prepping for the M&A announcement.