CHICAGO (AP) — A lawyer for former Republican Rep. Aaron Schock says prosecutors are aiming to be the first to imprison a former member of Congress over ambiguous rules the U.S. House set for itself.

Attorney Benjamin Hatch made the arguments Wednesday before the 7th U.S. Circuit Court of Appeals in Chicago as he seeks the dismissal of the corruption case against the former Illinois congressman Schock, who is charged with misusing government and campaign funds.

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A Department of Justice lawyer, William Glaser, says Hatch is mischaracterizing how prosecutors have approached the case. He says defense attorneys are effectively arguing that the Constitution bestows legal immunity on Schock, which it doesn’t.

Schock, of Peoria, made a rare public appearance at the hearing. He declined to comment as he left.

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Wednesday’s hearing at the 7th U.S. Circuit Court of Appeals comes amid signs parts of the case against the Peoria Republican may be at risk of unraveling.

Schock gained notoriety for redecorating his Capitol Hill office in the style of the “Downton Abbey” TV series. He was indicted in 2016 for misusing government and campaign funds. He’d resigned in 2015.

One question is whether prosecutors based charges on ambiguous House rules in violation of separation-of-powers clauses in the U.S. Constitution. Schock says they did, including with charges that he illegally sought reimbursements for a $5,000 office chandelier and other personal spending.

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