NASHVILLE − Kilmar Abrego Garcia, the Salvadoran immigrant at the heart of an international debate over President Donald Trump’s tougher border security policies, pleaded not guilty to charges of human smuggling.

U.S. Magistrate Judge Barbara Holmes in Tennessee was also hearing arguments June 13 about whether to keep Abrego Garcia, 29, detained while awaiting trial on charges he transported undocumented immigrants for financial gain.

Prosecutors, who allege he is a member of the crime gang MS-13, a designated terrorist organization, argued he could flee or intimidate witnesses if released. But Abrego Garcia, who denies belonging to the gang, argues the charges don’t justify being jailed.

Abrego Garcia has become a central figure in the debate over Trump’s tougher immigration enforcement. A longtime resident of Maryland, he was erroneously deported to a notorious prison in El Salvador on March 15 despite having an immigration court order preventing his removal. A federal judge in Maryland ordered the administration to facilitate his return, in a decision upheld by the Supreme Court, but officials resisted bringing him back until he was indicted May 21.

Related: How a traffic stop exploded into human smuggling charges for Kilmar Abrego Garcia