Agreed that it will be struck down like all of his unconstitutional decrees.
On what basis? Doing a little research, you might need to read the whole clause, added for you edification.
Federal requirements, via congressional acts, preempt conflicting state practices for federal elections.
The changes Congress enacted...
Article I Section 4 Congress Clause 1 Elections Clause
The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.
The SCOTUS has interpreted "manner" to include "notices, registration, supervision of voting, protection of voters, prevention of fraud and corrupt practices," etc.
H.R.3295 - Help America Vote Act of 2002
Directs the Administrator of General Services to establish a program for payment to each State that intends to use the payment in accordance with specified guidelines for activities to improve the administration of elections for Federal office. Designates permitted uses of such funds. Sets the size of the payment at an amount based on the voting age population plus a described minimum payment amount.
www.congress.gov
H.R.2 - National Voter Registration Act of 1993
The National Voter Registration was also enacted under the Elections Clause. It mandates that states maintain accurate voter rolls ("list maintenance"), offer registration at certain agencies, and accept a federal mail-registration form. Courts have upheld NVRA provisions as valid under the Elections Clause precisely because they target voter eligibility verification and roll accuracy.
www.congress.gov
Trump's EO does not create anything out of thin air; he's just implementing, and enhancing what Congress has authorized under existing federal statutory requirements using federal databases (SSA records, DHS's SAVE program). All of which are both HAVA and NVRA as authority.
The EO also authorizes withholding "federal funds from noncompliant states/localities where authorized by law." Congress can used the purse to encourage compliance without directly dictating state election codes, in the NVRA and HAVA.
The EO's core mechanisms operate using federal entities like the USPS, not state legislatures:
The EO is federal government is regulating its own property (mail) and funds, cleverly avoiding the anti-commandeering doctrine ... (Printz v. United States, 1997),
