Congressional Republicans, members of their staffs and conservative activists regularly flew first class to Saipan, an island just north of Guam in the Pacific Ocean. They slept at the beachfront Hyatt Regency, and dined on fresh Japanese cuisine.

The junkets in the late 1990s were organized by Patrick Pizzella. The Northern Mariana Islands, a commonwealth of the United States, had hired him to ensure that Congress did not impose federal minimum wage and immigration laws in a place where some workers earned less than $1 an hour.

Mr. Pizzella, a genial lobbyist and government official who has spent years advocating the interests of businesses, is set to become the top Trump administration official protecting workers’ rights when he takes over as acting labor secretary this week. He will fill the vacancy left when Alex Acosta resigned amid criticism of a plea deal he approved in 2008 with Jeffrey Epstein, the financier who has been accused of sex trafficking.

A longtime free-market evangelist, Mr. Pizzella, 65, has built a four-decade career in the conservative Republican mold, fighting regulation and organized labor.