The legal battle over horse slaughter in Illinois is moving forward. Attorneys for a suburban slaughterhouse want the U.S. Supreme Court to weigh in on the state’s ban against horse slaughter. They filed the petition yesterday.

The state of Illinois outlawed slaughtering horses for human consumption last year. That move essentially forced Cavel International in DeKalb to close its doors. Cavel was the last slaughterhouse of its type in the U-S.

It’s illegal to eat horse meat in the States - so Cavel had shipped the meat overseas. That’s key to Cavel’s legal argument. Phil Calabrese is an attorney for Cavel. He says the state ban violates federal and international trade laws.

CALABRESE: Under our Constitional system, foreign affairs, foreign commerce is reserved to the national government, to the federal government to regulate.

Calabrese says taking the case to the Supreme Court is Cavel’s last legal option. An attorney for the Humane Society of the United States—a long-time opponent of Cavel—says it believes the Supreme Court will reject the case, as it did a similar Texas case last year.