Washington (CNN) Washington Mayor Muriel Bowser says she'll defy congressional Republicans and implement D.C.'s new local law allowing its residents to smoke marijuana starting on Thursday.

In implementing the new pot laws, Bowser is rebuffing two influential House Republicans who'd warned her that she'd be breaking federal law -- and risking retribution.

"We would encourage the Congress to not be so concerned with overturning what seven out of 10 voters said should be the law in the District of Columbia," Bowser said at a news conference Wednesday afternoon.

Bowser and Washington police are implementing a measure approved by D.C. voters in November allowing Washington residents to possess up to two ounces of pot.

The allowance applies only to those over 21. In addition, D.C. residents could grow up to six pot plants in their own yards. Buying and selling pot would still be illegal, as would smoking in public places. But people could transfer up to one ounce to another person -- just not for money.

JUST WATCHED Washington D.C. to defy GOP, implement marijauna law Replay More Videos ... MUST WATCH Washington D.C. to defy GOP, implement marijauna law 02:45

House Oversight and Government Reform Committee Chairman Jason Chaffetz (R-Utah) and Rep. Mark Meadows (R-N.C.) said in a letter Tuesday that the city would be violating a spate of federal laws if it went forward with Bowser's plan to implement the new pro-pot measure Thursday.

"We strongly suggest you reconsider your position," the two wrote to Bowser -- while, in a thinly-veiled suggestion that there would be consequences for ignoring them, pointing to House rules that give Chaffetz's panel broad investigative authority.

Bowser, though, brushed Chaffetz and Meadows back on Wednesday, saying they should worry about bigger problems -- like funding the Department of Homeland Security, which is set to shut down at week's end if Congress doesn't act.

And she took a shot at Republicans who have suggested she could wind up in jail for breaking federal law -- even though Congress has no powers to prosecute her.

"A lot of reasonable people have a different view of this issue. ... I have a lot of things to do here in the District of Columbia, and me being in jail wouldn't be a good thing," she said.

It's the latest example of the strain between a heavily Democratic city that is ultimately controlled by a Republican-dominated Congress -- which couldn't stop similar marijuana legalization pushes in Colorado and Washington state, but is trying to use its power of the purse to do so this time.

Chaffetz and Meadows pointed to a provision included in a massive spending bill approved by Congress in December that prohibited Washington from legalizing marijuana, or cutting any drug possession penalties.

Bowser has insisted that the district's measure was enacted before that December vote. But the two Republicans noted that any bill in Washington can't become local law until it's been through a 30-day layover period before Congress. Until that happens, they said, the measure can't be considered enacted -- which in this case means it "was not enacted prior to the language in the continuing resolution preventing it from moving forward."

"If you decide to move forward tomorrow with the legalization of marijuana in the District, you will be doing so in knowing and willful violation of the law," Chaffetz and Meadows wrote.

Colorado, Washington and Alaska have so far legalized pot. But regulatory structures in those states are still being worked out, and under federal law, marijuana remains a Schedule 1 narcotic -- and therefore its use is a federal crime.

Still, Attorney General Eric Holder told CNN last year that he is "cautiously optimistic" that marijuana will be legalized, and that the Justice Department is focused on marijuana distribution to minors, interstate trafficking and drug violence, rather than "low-level people who are simply there for possessory offenses."

Twenty-three states still prohibit cannabis outright. The rest have either legalized medical marijuana or decriminalized marijuana possession.