Trump issued the order on March 25, 2025, and Ward Clark gave us an overview of what's in it:

The EO discusses the integrity of voter registration:

Within 30 days of the date of this order, the Election Assistance Commission shall take appropriate action to require, in its national mail voter registration form issued under 52 U.S.C. 20508:

(A) documentary proof of United States citizenship, consistent with 52 U.S.C. 20508(b)(3); and

(B) a State or local official to record on the form the type of document that the applicant presented as documentary proof of United States citizenship, including the date of the document’s issuance, the date of the document’s expiration (if any), the office that issued the document, and any unique identification number associated with the document as required by the criteria in 52 U.S.C. 21083(a)(5)(A), while taking appropriate measures to ensure information security.

And, there is a section strong-arming the states into strictly abiding by federal election laws:

The Election Assistance Commission shall, pursuant to 52 U.S.C. 21003(b)(3)and 21142(c) and consistent with applicable law, take all appropriate action to cease providing Federal funds to States that do not comply with the Federal laws set forth in 52 U.S.C. 21145, including the requirement in 52 U.S.C. 20505(a)(1) that States accept and use the national mail voter registration form issued pursuant to 52 U.S.C. 20508(a)(1), including any requirement for documentary proof of United States citizenship adopted pursuant to section 2(a)(ii) of this order. //

On Thursday, Kollar-Kotelly issued a 120-page memorandum opinion in support of her order granting the plaintiffs in the LULAC and League cases a preliminary injunction, prohibiting the administration from giving effect to section 2(a) of the order (requiring proof of citizenship in the national mail voter registration form). //

anon-15qo
15 minutes ago
Article II, Sec. 3, ...he [president] shall take Care that the Laws be faithfully executed,...
Article I, Sec. 4, of the Constitution gives states the responsibility of overseeing federal elections.
Amdt. 15, Sec.1, The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude–
Amdt. 19, The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex.
Amdt. 24, sec. 1, The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any State by reason of failure to pay any poll tax or other tax.
Amdt. 26, sec. 1, The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.