The enactment in late December of a law allowing paid parental leave for federal workers was hailed as an important new benefit for 2.1 million executive branch employees.

But upon further review, as a football referee might say, the number is lower. How much lower, and whether it will remain lower, is still to be determined.

The new law turns into paid time off the up to 12 weeks of annual unpaid parental leave currently available to federal employees, among many other American workers, under the Family and Medical Leave Act. It will apply to births, adoptions and foster placements on or after Oct. 1.

The House initially passed the benefit in July as part of a defense-spending bill. After the Senate narrowly defeated it, House-Senate conferees included it in a compromise that involved creating a new military Space Force, as President Trump sought.

Just days after that agreement, the House and the Senate passed the bill and Trump signed it, tweeting that the government “is leading by example in changing the culture of how we support working families.”

However, determining the exact impact of bill language involves slowing down and looking at it from many angles.

The language amends Title 5 of the U.S. Code, the standard set of civil service laws covering personnel policies, including leave.

Certain occupations and even some entire agencies fall under other sections of the law. The largest is the quasi-corporate U.S. Postal Service, with 600,000-plus employees. They were not added to the 2.1 million figure — the standard head count for the executive branch, apart from the USPS — because it was clear that the USPS was excluded.

Almost immediately, though, sponsors realized that the language as written would not cover some others. Those include the Federal Aviation Administration, which is under a separate section of the law called Title 49, and many medical personnel of the Department of Veterans Affairs, who are under a section called Title 38.

The Transportation Security Administration also operates mainly outside of Title 5; the new law specifically includes TSA screeners but not other TSA employees.

The FAA has about 44,000 employees. Tens of thousands more would be left out of the new benefit at VA and the TSA.

Just before Congress recessed in late December, Sen. Brian Schatz (D-Hawaii) sought to use a shortcut procedure to correct what he called a “technical and drafting error” to broaden the benefit to include those categories as well as federal judges and many political appointees, who also are excluded. However, that bid died when Republicans moved to pair it with an unrelated tax measure.

Schatz’s bill is pending in Congress, as is a separate House bill that would apply only to the FAA. Neither is currently scheduled for a vote.

According to an analysis by the National Air Traffic Controllers Association (NATCA) — whose members, as FAA employees, are among those excluded — U.S. Public Health Service officers also are left out, as are financial regulatory agencies that operate under the Financial Institutions Reform, Recovery and Enforcement Act.

Patricia Gilbert, executive vice president of the NATCA, said in a phone interview that technical errors are “unfortunate but not uncommon” when legislation moves quickly. But she said the union is hopeful the law will be broadened because “the intent of the language was to cover the entire federal workforce.”

Even if the law is not changed, VA intends to extend the benefit to its Title 38 employees, spokeswoman Susan Carter said in an email. “Per federal law, VA has the discretion to permit Title 38 employees to have the same benefits as other VA employees. This is what VA plans to do with the paid parental leave provision,” she said.

The Office of Personnel Management will issue regulations and guidance to implement the legislation, she said. After that, VA will establish a policy for all employees — including Title 38 employees — to use the benefit.

Gilbert said the FAA and other agencies could voluntarily begin a paid parental leave policy, but “into the future, when it’s not mandated in law, would they keep it in place? The weight of law is much stronger.”

For example, she said, an agency might try to use the benefit as a bargaining chip in future negotiations with a union.

Two agencies that have implemented paid leave policies are the Securities and Exchange Commission and the Federal Deposit Insurance Corporation, both of which provide for six weeks of paid parental leave, following recent bargaining with the National Treasury Employees Union (NTEU).

Those programs remain in place until the new 12-week program takes effect in October. “At that point the larger government-wide program kicks in, although NTEU retains the option of negotiating over any differences that may exist between the two programs,” Tony Reardon, the union’s president, said in an email.

For other agencies, the delay in the effective date until October leaves time for Congress to act, and “we urge Congress to use this time to correct the technical oversight and ensure that all federal employees are treated equally under the law,” Everett Kelley, secretary-treasurer of the American Federation of Government Employees, said in an email.

The Office of Management and Budget did not respond to a request for comment.