The impartial conduct standards that will go into effect at 11:59 p.m. on June 9 require that advice providers to IRA and 401(k) investors act in the best interest of investors, receive only reasonable compensation, and not make misleading statements to investors.

In his decision to keep implementation of those standards in place, Sec. Acosta said there were limited options to issue a delay to the June 9 requirements under the Administrative Procedure Act, the statute that governs federal rule-making.

“From the consumer perspective, this is a huge win,” said Rob Foregger, co-founder of Chicago-based NextCapital, which provides digital advice platforms for 401(k) and retail investment advisors. “It is imperative that the retirement industry provides transparent and cost-effective financial services, which align with the client’s best interests.”

While Foregger and other proponents of the rule are heartened by Acosta’s decision to not flout the notice and comment requirements under the APA and issue another delay, there is the chance that this week’s news will only prove a Pyrrhic victory for fiduciary advocates.

Acosta’s opinion editorial explaining his decision to keep the June 9 implementation date in place, and an FAQ published by the agency on the same day, leave the door open for a delay of the January 1, 2018 full implementation date, and even the possibility that the rule’s existing compliance requirements and enforcement mechanisms are substantially revised.

Advocates of the fiduciary rule have expressed concern that could lead to a watered-down rule—an un-enforceable fiduciary standard in name only.

In the op-ed, Acosta noted the importance of retirement investors’ need for prudent advice but said the rule as currently written “limits choice and benefits lawyers.”

That unsubtle hint suggests the rule’s provision that allows investors to bring class-action lawsuits against investment providers will have to stand up to new scrutiny. Obama administration regulators openly touted that provision as the rule’s primary enforcement mechanism.

For the time being, the plaintiffs’ bar should be kept at bay, as written warranties of fiduciary status, and the rule’s Best Interest Contact Exemption, which includes the class-action provision, are not required until the first of next year.

Moreover, Labor signaled it would not be enforcing even the impartial conduct standards until January 2018, so long as firms are working “diligently and in good faith” to give fiduciary advice.

That “essentially ensures that neither the DOL nor private litigants will be able to bring a lawsuit to enforce the rule until after January 1, 2018,” said Erin Sweeney, an attorney with Miller & Chevalier, in a statement.

After that date, all bets are off, assuming the January 1, 2018 deadline holds up. In the most recent Labor FAQ, regulators raised the prospect that a delay of the full rule would allow for “more affective retirement investor assistance” as industry completes the rollout of new investment products, like so-called clean shares of mutual funds designed to mitigate advisor conflicts.