The move comes a week after a U.S. House panel voted largely on party lines to advance a measure that would repeal the city's Death With Dignity Act. That language must be approved by the full House and Senate, and by President Trump, before it can take effect.
The assisted-suicide law, passed 11 to 2 last year by the D.C. Council after more than a year of debate, is the latest District measure targeted by federal lawmakers, who have previously moved to block needle exchanges, the legalization of marijuana and abortion subsidies for low-income women.
Congress has broad authority to intervene in the District's lawmaking and spending under the Constitution and the federal act that allows the city to govern itself.
"We execute the laws that the council passes, and at this point, this is the law in the District of Columbia," said John Falcicchio, chief of staff to Mayor Muriel E. Bowser (D). "We don't stop just because there's a threat of congressional riders."
The D.C. Health Department on Monday launched a website where physicians can register to participate in the "Death With Dignity" program, and where doctors, pharmacists and patients can read up on the law's requirements and download related forms.
Patients must be older than 18 with less than six months to live to be eligible. They must make two requests at least 15 days apart for life-ending medications and ingest the drugs themselves. Two witnesses must attest that the patients are making the decision voluntarily.
The law requires the city government to track such requests. In general, it is expected to take at least three weeks for a patient to receive life-ending medications after beginning the process.
The assisted-suicide law has faced multiple opponents, including a contingent of House Republicans, since Bowser signed it late last year. Trump's budget proposal prohibits funding for the D.C. law, which was supposed to take effect beginning in late September.
The quick action by city officials to roll out the "Death With Dignity" program on Monday is aimed at preventing federal lawmakers from blocking such spending.
In a letter to Sen. James Lankford (R-Okla.), a critic of the assisted-suicide law, Bowser said that no federal funds were used to implement the law and that none will be needed.
It's unclear whether future expenditures, such as staff time to compile statistics and accept forms, could be subject to congressional prohibitions.
The "right-to-die" movement has gained momentum in recent years, with measures passed by lawmakers in California and voters in Colorado, and dozens of proposals introduced in other state houses, including in Maryland.
Advocates say patients facing impending death should have the right to die on their own terms and avert needless pain.
But social conservatives have assailed the practice as undermining the sanctity of life, while advocates for people with disabilities are raising concerns that patients could be pressured into ending their lives early.
Rep. Andy Harris (R-Md.), a longtime antagonist of the District and a staunch opponent of assisted suicide, sponsored the amendment to quash the D.C. law, which he calls "poorly written" and "misguided."
After fellow Republicans failed to pass a resolution that would have stopped the bill from becoming law, Harris introduced an amendment to a financial services appropriations bill that would repeal the law outright.
A spokeswoman for Harris suggested that the Bowser administration's efforts on Monday were moot.
"The congressman's amendment repeals the law, so while D.C. could implement the Death With Dignity Act, it would be repealed once the appropriations process is complete and the bills are passed," said Jacque Clark, the spokeswoman.
Del. Eleanor Holmes Norton (D-D.C.) said she will try to strike all District-related measures when the budget bill goes to the House floor.
"We will continue to fight those attempts to overturn or undermine our laws with Congresswoman Norton and other allies in Congress," Falcicchio said.