Several Supreme Court justices struggled Monday to define when obstruction of justice becomes a deportable offense, with Justice Clarence Thomas invoking mythical sea monsters to suggest the court must choose the lesser of two evils.

Throughout the nearly two hours of oral arguments from two convicted men who, on one hand, say such felonies require interference with active law enforcement investigations, and the Biden administration, on the other hand, which says that a pending proceeding is not necessary, the justices didn't seem convinced by the strength of either party's arguments.

Justice Thomas compared the court's path forward to the perilous maritime journey between the sea monsters Scylla and Charybdis in Homer's Odyssey. In the poem, Odysseus chooses to pass near Scylla, who eats six of his men, rather than risk losing his entire ship to Charybdis.

"I think the problem that we're having is that the government wants to broaden the definition. It's like we're navigating between Scylla and Charybdis, and no one is giving us a way to get between the two extremes," Justice Thomas said.

In urging the justices to adopt the broader view, U.S. Department of Justice attorney Curtis E. Gannon said "the wheels of justice can be obstructed, even before they begin to move."

But Mattie Hutton of O'Melveny & Myers LLP, who represents Jean Francois Pugin, one of the two men fighting deportation, said that offenses related to obstruction of justice must have a nexus to a pending proceeding to be considered aggravated felonies for the purposes of removal under the Immigration and Nationality Act.

The core of what is meant by "pending proceeding" pertains to judicial actions, Hutton said, but doesn't necessarily exclude other official proceedings. Justice Thomas pressed Hutton on how to confine that, asking whether an investigation would count as an official proceeding.

"An investigation is a step further out from the core definition and so should be viewed with some caution, but I don't think we would object necessarily to it being used here," Hutton said.

But Justice Thomas was not satisfied.

"You're saying you would like to restrict it to a pending proceeding, but as we drift away from the core — that is, judicial proceedings ... you're not giving us a way to navigate how far out do we go," he said.

The Biden administration's argument largely aligns with the Board of Immigration Appeals' separate decisions to remove Fernando Cordero-Garcia, a permanent resident since 1965 who had been convicted of stopping a victim from reporting sexual abuse, and Pugin, a green-card holder since 1985 who had been convicted of being an accessory after the fact to a felony.

The board held both as removable under Section 1101 of the INA, which defines a deportable aggravated felony as "an offense relating to obstruction of justice ... for which the term of imprisonment is at least one year." The Fourth Circuit upheld Pugin's removal order, but the Ninth Circuit overturned Cordero-Garcia's, teeing up a circuit split for the justices to address in the two consolidated cases.

Like Justice Thomas, Chief Justice John Roberts appeared perplexed during Monday's arguments about where to draw the line, saying he was particularly troubled by the "relating to" language in the INA provision at issue. That language implies that the definition of obstruction of justice is broader than the definition that Pugin and Cordero-Garcia put forward, he said.

Gannon said that the "relating to" language does broaden the scope beyond the core obstruction of justice crimes, and that a requirement to find intent behind interference with proceedings of law and justice limits the scope from becoming too broad.

"Even though it would need to relate to obstruction of justice, we think, to the extent that there is a specific intent to interfere, that's a sufficiently close nexus that you don't need to be concerned about sweeping in a lot of other offenses," he said.

To support its argument that a pending proceeding is not necessary for offenses related to obstruction of justice, the Biden administration had pointed the justices in a February filing to Section 1512 of Title 18 of the U.S. Code, which deals with witness tampering and does not require a nexus to a pending proceeding.

But Justice Neil Gorsuch wondered if that might actually cut against the government since Congress went out of its way to say that no pending proceeding is required in that instance.

"Isn't it the exception that proves the rule?" he asked.

Gannon dismissed that as Congress trying to distinguish that provision from another dealing with threats to jurors or court officers.

The Biden administration's position drew opposition from immigration-focused organizations that argued in amicus briefs that it would impose the harsh penalty of deportation for low-level state-law offenses, many of which are considered misdemeanors in most U.S. states, like impeding government operations, failing to report a crime or presenting fake identification documents.

Pugin is represented by Michael R. Dreeben, Brian D. Boyle, Mattie Hutton, Jenya Godina, Jack Derewicz, Bruce Pettig and Lauren Averill of O'Melveny & Myers LLP.

Cordero-Garcia is represented by Mark Christopher Fleming, Michael S. Crafts, Victoria L. Moreno, Jason F. Choy, Michael E. Romeo, Joshua A. Vittor, Catherine M.A. Carroll and Allison M. Schultz of WilmerHale, and Michael K. Mehr of Mehr & Soto LLP.

The government is represented by Elizabeth Prelogar, Brian M. Boynton, Curtis E. Gannon, Frederick Liu, John W. Blakeley and Aimee J. Carmichael of the U.S. Department of Justice.

The cases are Garland v. Cordero-Garcia, case number 22-331, and Pugin v. Garland, case number 22-23, before the Supreme Court of the United States.

--Additional reporting by Micah Danney and Rae Ann Varona. Editing by Adam LoBelia.