A group of 17 former Department of Interior (DOI) officials that served under every presidential administration since Richard Nixon is voicing concern over the Trump administration’s new legal interpretation of the Migratory Bird Treaty Act (MBTA).

MBTA stipulates, among other things, that it is illegal to “pursue, hunt, take, capture, kill, attempt to take, [or] capture or kill” migratory birds “by any means whatever…or in any manner,” unless permitted by regulations. The issue is an important one for onshore oil and natural gas producers, as they look to minimize the impact their operations have on birds, including the greater sage grouse and the lesser prairie chicken.

In a 41-page opinion released last month, DOI’s Daniel Jorjani, principal deputy solicitor, said MBTA’s prohibitions only apply to “direct and affirmative purposeful actions that reduce migratory birds, their eggs, or their nests, by killing or capturing, to human control.”

In a letter to Interior Secretary Ryan Zinke on Wednesday, the former DOI officials called Jorjani’s interpretation of MBTA “contrary to the long-standing interpretation by every administration (Republican and Democrat) since at least the 1970s…”

“This is a new, contrived legal standard that creates a huge loophole in the MBTA, allowing companies to engage in activities that routinely kill migratory birds so long as they were not intending that their operations would ‘render an animal subject to human control.'”

The signatories said they had worked with oil producers “to ensure that exposed crude oil waste pits were covered with nets to keep birds from landing in them.” They urged the Trump administration to follow their lead in striking “a balance between development and conservation.”

MBTA was enacted in 1918, following a 1916 agreement between the United States and Great Britain, acting on Canada’s behalf, to protect the birds. Amendments were tacked on to MBTA following separate treaties between the United States and Mexico (in 1936), Japan (1974) and the Soviet Union (1978), now Russia.

In 2015, Interior’s U.S. Fish and Wildlife Service announced plans to prepare a programmatic environmental impact statement (PEIS) on MBTA. Specifically, the PEIS was intended to strengthen MBTA by addressing threats to birds posed by natural gas flares and uncovered waste oil pits, as well as unprotected power lines and communications towers.