Three documents, read together, describe a deadline that cannot be met.
The order. Executive Order 14399, published at 91 Federal Register 17125, directs that any final rule issued under section 3 come 'no later than 120 days from the date of' the order [3]. That is Wednesday, July 29.
The absence. As of Monday morning the Federal Register's public-inspection list - the queue documents enter before they publish - held 98 documents, every one filed on July 23 or July 24. The only postal items in it are routine Postal Regulatory Commission filings on new products and product lists [1]. There is no Postal Service rule of any kind in the queue, two days out.
The Postal Service's own paperwork, which settles the question. On July 17 USPS published a Privacy Act notice creating a new system of records, USPS 820.225, 'Federal Ballot Mail.' It would hold, for people receiving federal mail ballots, their name, address, unique IMb barcode numbers and originating election-office state, along with portal credentials, sourced from state-provided lists and retained five years [2].
The notice states that the system becomes effective only if USPS issues a final rule following relief from the existing court injunctions [2]. The proposed rule says the same in its own words: it is 'subject of active litigation, including two injunctions that are currently being appealed' [3].
That relief was denied. On July 25 a First Circuit panel denied emergency stay motions from the administration and twelve intervenor states, leaving USPS barred from finalizing mail-ballot envelope rules in 23 states and the District of Columbia through November 3 [4].
The sequence is therefore: an order requiring a rule by Wednesday, a rule that cannot take effect without relief, and relief refused on Saturday.
What the rule would do is worth stating, because a deadline is only interesting if the thing behind it matters. Under the proposal, states must upload voter names, addresses and barcodes to a Federal Ballot Mail Portal at least 30 days before an election, and USPS 'would verify... that recipients are enrolled on state participation lists before acceptance' [3].
A ballot addressed to someone not on the federal list does not get delivered.