Legislation making its way through Congress could have a damaging impact on future US offshore oil and gas projects.

The Coast Guard Authorization Act of 2019 could prohibit foreign-flag heavylift crane vessels capable of hoisting 1,000 tonnes from performing the cargo-laden short movements necessary to build offshore. Unless waivers can be obtained, that could scuttle new projects.

“For a few years now, since at least 2012, there has been some confusion in the industry about short movements, or what people would consider de minimis movements, of heavylift vessels,” said Washington-based...